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1 Physics Paper - I Answers Section - A Answer 1 1. The base ball will have maximum velocity when it reaches the ground. It will have minimum velocity when it reaches its maximum height.. A body is said to have acceleration when its velocity, direction or both change. 3. a) uniform retardation b) uniform velocity. 4. maximum velocity = 10 ms -1 when it returns to the ground. minimum velocity = 0 time of ascent = 1s (v = u - gt) o = (t) time of descent = 1s t = 1s. Answer 1. MSR =. 45 cm CVD = 4 LC = 0.1 = 0.01 cm 10 = 0.01 x 10 - m = m or 1 x 10-4 m. diameter = MSR + (CVD x LC) =. 45 cm + (4x 0.01) = =. 49 cm. diameter of the bob =. 49 x 10 - m. a) 10-4 m b) kg. 3. a) Joule b) ms -1 c) J kg -1 k -1 d) N s m distance moved on the pitch scale Pitch = Number of rotations given 10mm = 5 = mm. Pitch Least count = Number of Head scale divisions mm = 50 = 0.04 mm. Answer 3 1. a) Gravitational force between two bodies. b) Electrostatic force between charges.. Scalar quantity : A physical quantity which has only magnitude but no direction. e.g: mass, time. Vector quantity : A physical quantity which has both magnitude and direction. e.g.: force, acceleration. 1

2 3. Mass m = 3 kg force F = 18 N F = ma a = F / m = 18 3 a = 6 ms - 4. The quantity of motion contained in a body. It is measured by the product of mass and velocity. It acts along the direction of force. SI unit of momentum is Kgms -1. Answer 4 : 1. The force acting normally on a surface of a body in contact with a liquid. Its SI unit is N.. a) Density of a liquid (p) b) Acceleration due to gravity (g) 3. The pressure exerted anywhere in a confined liquid is transmitted equally and undiminished in all directions throughout the liquid. Applications: 1. Hydraulic press.. Hydraulic lift. 4. a) W > W 1 b) W = W 1 c) W < W 1 5. Pascal or pa. Section - B Answer 5 1. As the moisture in air increases, the density of sound decreases. Velocity of sound is inversely proportional to density of the medium. Therefore the sound travels faster in humid air.. g = 4 π - L T given, L = 60 cm = 0.6 m; T =?, g = 9.8 ms = 4 x 3.14 x 3.14 x T 4 x 3.14 x 3.14 x 0.6 T = = T=.414 = 1.55s. 3. SONAR : Sonographic Navigation and ranging use: Dectection of defects in metals. Distance travelled by a wave 4. Velocity = Time λ wave length v = = T time period

3 But we know that T = 1 1 = f frequency 5. v = λ.f v = fλ. Sl. No. Transverse wave Longitudinal wave 1 The energy transfer is perpendicular to the direction of propogation. The energy transfer is along the direction of propogation. They propogate in the form of crests and troughs They propogate as compressions and rarefractions. Answer 6: 1. The image A 1 B 1 is formed between C and F at a distance of 10.9 cm from the pole.. Infinite number of images. 3. A mirror of length equal to half his height. 4. a) As a shaving mirror b) As a reflector in torch, search light, head light etc. 5. a) 3

4 b) c) Answer 7 1. a) vernier callipers. b) upper jaws of vernier callipers. c) stop clock d) depth probe of vernier callipers.. Reflection at the two parallel plane mirrors facing each other and each kept inclined at an angle of 45 o with the vertical. 3. Uniform velocity : The body covers equal distances in equal intervals of time however small the intervals may be. Average velocity : It is the ratio between the total distance travelled by the body and the total time taken. 4. a) Velocity of light = ms -1-8 Distance travelled by light in 30 days = 30 x 4 x 60 x60 x 3 x 10 = 7.77 x m. b) Velocity of sound at 0 O C = 331 ms Hour = 3600 s. Distance travelled by sound in 1 hour = 3600 x 331 = x 10 6 m. 4

5 Answer 8 1. p = 1.04 x 10 5 pa ; g = 10 ms - ; p air = 1.3 p = Pgh height h = P 5 pg = 1.04 x 10 = 8000m. 1.3 x 10. a) Reading becomes inaccurate as water sticks with glass. b) Density of water is low for water. That makes the height of the tube very high. 3. Buoyant force F = volume x density x acceleration due to gravity. = v pg. v = 5 x 5 x 5 = 1565 x 10-6 m F = 1565 x 10 x 9.8 x 1000 = N. 4. Let the volume of wood be V Let the density of wood be P Volume of wood above the surface ( 1 ) = v 5 volume of wood beneath the surface of water = = v 1 v= 4 v 5 5 Density of water = 19cm -3 = 1000 kgm -3. By the principle of floatation, weight of block = weight of water displaced by the immersed part of the block. 4 v x p x 9.8 = v x 1000 x p = x 1000 = 800 kgm 5 density of wood = 800 kgm a) It is the centre of gravity of the displaced liquid through which the resultant upthrust acts. b) The weight of the floating body is equal to the weight of the liquid displaced by its sub merged part. Answer 9 1. Co- efficient of cubical expansion γ = 3 x coefficient of linear expansion γ = 3 x α α = γ x 10 = 3-5 o -1 α = 1.7 x 10 C. The expansion of water when it is cooled from 4 o C to 0 o C is known as anomalous expansion of water. This helps in preserving the aquatic life during very cold weather. 3. C F - 3 = 5 9 5

6 5(98.4-3) 9 In Kelvin scale = = K o o o 98.4 F in C = = 36.9 C o 4 a) Room are provided with ventillators near the ceiling. The cold fresh air from outside enters in the room through doors and windows replacing the warm, lighter ventilated air. b) The warm air rises up and cold air from above comes down to take its space. Answer a) charges are shared. b) An ion is an atom which has either gained or lost one or more electrons.. It is a device used to detect the presence of charge and to identify the nature of charge on a body. 1. Pith pall electroscope.. Gold leaf electroscope. 3. A - cell. B - ammeter. C - resistance. D - voltmeter. E - rheostat. F - plug key. 4. (i) Area of cross section. (ii) 6

7 Answer 1 Physics Paper - Answers Section - A 1. Displacement Velocity = time Displacement = 300 km time = 0 minutes 0 = Hour = 1 Hr Velocity in kmh = -1 Velocity in ms = = 300 x 3 = 900 kmh 900 x x 60-1 = 50 ms.. Equal changes in velocity takes place in equal intervals of time a) 7

8 b) Distance covered during uniform & acceleration = Area of Δ OAC c) Change in velocity retardation = time interval 0 10 = 10 - = 1 ms 5. Time of ascent t = 5 =.5s. - g = 10 ms ; v = 0; u =? Solution : v = u - gt 0 = u - 10 x.5-1 u = 5 ms v = u - gh o = u - (10)H 65 = 0 H H = 65 = 31.5 m 0 = 1 x 10 x 10 = 50 m v = 0 ms ; 1 m = 10 km; 1s = -1 0 ms in kmph = Answer 1. a) Dusting off a carpet x = 7 kmph. hour b) Fruits falling off a tree when it is shaken.. Momentum = mass x velocity = 9 x x 5 x 10 7 = 45 x 10-4 kgms F = 15 N; m = 500 x 10-3 kg; t = 10s; u = 0, v =? Solution: F = m x a 15 = 500 x 10-3 x a -3 a = 15 x a = 30 ms 8

9 v u (i) But a = t v 0 30 = t -1 v = 300 ms 1 ( ii) s = ut + at = (0) t + 1 (30)(10) = 1500 m s = 1500 m. 4. F = 400 N; m = 5 x 10-3 kg; u = 400 ms -1 ; v = 0; t =? Solution: Force offered by the wooden plank to stop the bullet = F = ma = 400 N 400 retardation of bullet = [ Q a = F/m] -3 5 x = x 10 ms But a = x 10 = v - u t t -3 t =.3 x 10 s. 1 But s = ut + at = 400 x.3 x 10-1 (1.68 x 10 ) x (.3 x 10 ) = Distance travelled by the bullet s = 0.48 m. 5. The force of attraction acting between two particles is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Unit of universal Gravitational constant is Nm kg -. Answer 3 1. Car radiators work on the principle of convection currents. The hot water circulating around the engine expands and flows into the radiator. It becomes cold and heavy after dissipating its heat. Then again it flows back to engine.. (i) Trade winds. (ii) Westerlies. (iii) Polar winds. 3. a) We wear white clothes in summer as they are good reflectors of heat. b) Cooking utensils are black at the bottom and shining at the sides. 4. a) Cloudly nights are warmer as they reflect the heat energy back to earth. Whereas on 9

10 clear nights, the warmer air is replaced by the cold air. b) Dirt absorb heat energy from the sun faster whereas clear snow contains more water which takes longer time. c) White clothes are good reflectors of heat. Answer 4 1. Real image : The image that can be obtained on a screen. Virtual image : The image which cannot be obtained on a screen.. a) Pole : The geometric centre of the spherical surface of the mirror. b) Aperture : The area available for reflection for a spherical mirror. c) Focal length : The distance between the pole and the priniciple focus of a spherical mirror. d) Radius of curvature :The radius of the sphere in which the spherical mirror becomes a part. 3. a) real. b) inverted. c) enlarged. d) formed beyond C. 4. When an object is placed between P and F of a concave mirror, it forms a virtual, enlarged and erect image. 5. At the centre of curvature. Answer 5 1 a) grams. b) milligram. Section - B. a) kg b) 10 6 m c)10-6 kg d) 10-3 s. 3. L.C. = 0.01 cm. Z E = +5 = +5 x 0.01 = cm M S R = 8.40 cm. CUD = 7 TR = MSR + (CVD LC) 10

11 TR = 8.40 cm + (7 0.01) TR = 8.47 cm. Corrected Reading = TR - ZE = Diameter of the cylinder = 8.4 cm. 4. Number of Head scale divisions = 100 distance moved 1 mm Pitch = = = 0.5 mm. number of rotations pitch Least count = number of head scale divisions 0.5 mm = 100 L.c =.005 mm. 5. a) A simple pendulum whose time period is s. b) (i) length (ii) acceleration due to gravity. Answer 6 1) a) Velocity = f λ frequency f = v λ 3 x 10 = 800 x 10 b) 1 1 T = = = 3.75 x 10 Hz. f 3.75 x = 0.66 x 10 s -16 Time period T =.66 x 10 s λ = 100 cm = 100 x 10 m; f = 000 Hz λ = 15 x 10 m. f =? 15 We know that v = fλ (i) velocity = v = f1λ1 = 000 x 100 x 10-1 = 000 ms. (ii) New - frequency = f1λ 1= fλ 000 x 100 x 10 = f x 100 x 10 f = - 15 x 10 = 1600 Hz

12 3. Time taken for 100 waves = 1 minute = 60 s 60 3 (i) Time taken for 1 wave = = Time period of wave = 0.6s. (ii) - Wave length = λ = 4.5 x 10 m Wave velocity v = λf = λ T 4.5 x 10 = = 7.5 x 10 ms. 4. Bats produce ultrasonic waves. By hearing the reflected sound and from the time interval, they can judge the distance of the obstacle on their way. 5. (i) medium must be elastic. (ii) medium must have inertia. Answer 7 1. a) The flow of electrons from a region of lower potential to a region of higher potential is called electric conduction. b) The phenomenon due to which an insulated uncharged conductor gets electrically charged when held near a charged body is called electrostatic induction.. Q = 100C, t = minutes = x 60 = 10 s. I = Q = 100 t 10 I = 0.83 A Geographic meridian : It is the vertical plane containing geographic north and south poles of the earth at a given place. Magnetic meridian : It is the vertical plane containing the magnetic axis of a free suspended magnet at rest, under the action of magnetic intensity of the earth. 1

13 Answer a) They are closed curves. They start from the N-pole and end in the S-pole. b) Lines of force repel each other. 4. The magnetic need of a mariner s compass shows the magnetic north-south rather than geographic north-south direction. It has a knowledge of declination, the navigator can adjust his direction. 5. a) steel has higher magnetic retention. b) They cannot be magnetised to a very high degree. 6. No two lines of force will cut each other, because in that case there would be two directions of resultant magnetic force at a given point, which is not possible. Answer 9 1. P = pgh; p = 0.80 x 10 3 kgm 3 ; g = 10 ms - ; h = 1 m = 0.80 x 10 3 x 10 x1 Pressure P = 8000 pa.. p water = 1000 kgm -3 ; g = 10 ms - ; Pressure of water due to height of 5 m h = hpg = 5 x 1000 x 10 = 50,000 pa. Pressure in the water pipe on the I floor = 1,00,000-50,000 = pa. 13

14 3. (i) weight of solid in air R.D of solid = weight of solid in air - weight of solid in water. (ii) = = 0.03 = Density of solid R.D of solid = Density of water Density of solid = R.D of solid x density of water = 5.33 x = 5330 kgm. 4. Whenever any pressure is applied to any part of the boundary of a confined fluid, it is transmitted equally in all directions irrespective of the area on which it acts and always acts at right angles to the surface of containing vessel. 5. Weight of water displaced by the iron nail is less than the iron nail. Ship displaces more mass of water than its own mass. Answer a) t = t = 348 K. F - 3 b) = C 9 5 F - 3 = 9 C 5 = 9 x F = o t = 167 F. a) A small gap is left between the successive lengths of rail as during summer steel will expand. b) Electric cables and telephone wires expand in summer and contract during winter. To prevent this these cables are laid low with less tension. 3. Increase in length = (L - L ) = L x α x t 0 0 L - L = x 10 m L =? L - L0 L 0 = αt - x 10 (600-5) = 15 x 10-6 x 14

15 x 10 - = 15 x 10-6 x 575 =.3 m. 4. Anomalous expansion of water. 5. a) They travel with the velocity of light. b) They travel through 15

16 Physics Paper - 3 Answers Section - A Answer 1 1. a) When a body does not change its position with respect to the surroundings. b) When the body changes its position with respect to the surroundings.. The acceleration of a freely falling body, under the action of gravity of earth is called acceleration due to gravity. Its value is 9.8 ms Speed = 100 kmh x 1000 Speed in ms = 60 x 60-1 = 7.78 ms. distance 4. velocity = time distance = velocity x time = 70 x 3 Distance between Bangalore & Mysore = 10 km. 5. a) 4 second b) a = = - ms. 1 c) Area of the ΔOAC = x 6 x 4 = 1 m. Answer 1. The instantaneous force which a body possesses due to combined effect of mass and velocity is called linear momentum. Its SI unit is kgms -1.. Force; Newton. 3. m = 500 kg speed = 60 kmh = = ms t = 10s Retardation = 10 r a = ms r Force applied by brakes F = ma = 500 x 1.66 = 830 N. 16

17 4. Mass is an intrinsic property of matter. It is a scalar quantity. The force with which a body is attracted towards earth is called its weight. It is a vector quantity. 5. This is due to Newton s third law of motion. F 1 = -F Force exerted by the bullet on the gun = Force with which the gun holder holds it. Answer 3 1. F 1 = 15 N; A 1 = 00 x (10 - ) = 00 x 10-4 m ; F =? A = 300 x 10-4 m ; According to Pascal s law, F 1 A 1 = F A FA 1 1 F = A x 00 x 10 = x 10 F = 10 N.. a) Hydraulic lift. b) Hydraulic press. 3. a) altitude b) acceleration due to gravity. 4. P = pgh P Hg = 13.6 x 10 3 kg m -3 g = 9.8 ms - h = 15 x 10-3 m P = 13.6 x 10 3 x 9.8 x 15 x 10-3 P = x 10 3 pa. = 000 pa. 5. Pressure P = 5 pa Area of the force A = 5 x 5 = 5 cm = 5 x 10-4 m. Thrust exerted F = Pressure x Area = 5 x 5 x 10-4 = 15 x 10-4 = 1.5 x 10 - N. Answer 4 1. An atom is the smallest particle of an element which may or may not have an independent existence but always takes part in a chemical reaction. An ion is an atom which has either gained or lost one or more electrons. 17

18 . Q = +5 mc Q = ne + 5 x 10 n = 1.6 x = 3.15 x 10 electrons deficit It is a device used to protect large buildings against lightning during a thunder storm. It is made of copper. 5. q = 1.6 x C. 6. In nature charge always occurs on an integer multiple of electronic charge. Q = ± ne. 1. Section - B i + r = 90 o glancing angle of incidence = ONP = 90 - MNP = o ONP = 45.. Image shifts 60 cm from its previous position. 18

19 3. a) b) 4. Radius of curvature = x focal length R = f. 5. a) Concave mirror b) Plane mirror c) Convex mirror. Answer 6 1. Sl.No Transverse wave Longitudinal wave 1. Energy transfer is perpendicular to the direction of propagation. Energy transfer is parallel to the direction of propagation.. Example : Light waves. Example : Sound waves. distance travelled. velocity = time = λ T But T = 1 f v = λf v = λf 3. As the temperature increases the velocity also increases. As the humidity increases the velocity increase too. 19

20 4. Time taken for 50 waves = 0.5s 0.5 Time period of a wave = 50 T = 0.01s. frequency f = 1 T = 100 Hz 5. From 0 Hz to 0000 Hz ms -1. Answer 7 1. Sl.No Heat Temperature a. b. Heat is a form of energy which causes the sensation of hotness or coldness. It is the sum of kinetic energy and potential energy of all the molecules of the given substance. It is the degree of hotness or coldness of a body. It is the average of the kinetic energies of all the molecules of a substance.. During the summer they expand. Hence the wires sag. During winter they contract. Hence they become tighter. 3. Because of thermal expansion during summer and contraction of the hands during winter L' = L o + L o; α = c 100 L' - Lo α = Lt o 0.5 L+ o L o - Lo 100 = Lt o 0.5 Lo 1+ -Lo 100 α= Lt o o -1 0

21 α = 0.5 Lo Lt o t = = o t = 50 C o It should be heated through 50 C. 5. Temperature difference between dry ice and steam = 100 o C. Length of mercury thread = 1 cm. 1 length of 1 thread = 100 = 0.1 cm. 6. a) Bimetallic strips b) Thermostat. Answer 8 1. Weight in air = 300gf Weight in water = 00gf a) Loss of weight of the body = 300gf - 00gf = 100gf b) Upthrust on the body = loss of weight = 100gf.. When a body is partially or completely immersed in a liquid, the body experiences an upthrust which is equal to the weight of the liquid displaced by it. 3. Centre of buoyancy is the centre of gravity of the displaced liquid through which the resultant upthrust acts. Density of the substance 4. Relative density(r.d.) = (p o 5) Density of water at 4 C p = 1000 Density of silver P = 1000 x 10.8 Ag -3 = kgm. 5. Hydrometer is a devised used for measuring densities of liquids accurately. It works on the principle of floatation. Answer 9 1. Joule, Newton μg = 10 kg 1

22 1 fermi = m. 3. Pitch = 0.5 mm Number of Head scale divisions = 50 Pitch Least count = number of Head scale divisions 0.5 = mm = mm Due to wear and tear, the tip of the screw will not be moving in the opposite direction while reversing the direction of the screw head. This is called backlash error. To rectify this error, the screw must be rotated in one direction only. 5. When a simple pendulum is taken to the moon, its time period will increase. ie g' = g [g' - acceleration due to gravity on the moon] 6 g' = 4π L T' T' = 4π L g' L T' = 4π 6 = 4π L g' g' It increases. Answer Q = 1 μc = 10 C I = q t 6 10 = 10-7 = 10 A = 0.1 μ A. joule. volt = coulomb 3. a) resistance becomes twice. b) resistance becomes one fourth. 4. a) When a magnetic needle is freely suspended, it always rests in geographic north-south direction. b) When an iron rod is buried deep into the earth, after a while it becomes a magnet if it is buried in the north-south direction. 5. The pieces of lodestone found in nature are called natural magnets. Artificial magnet is a magnetised piece of

23 Answer 1 Physics Paper - 4 Answers Section - A 1. a) Area of the velocity - time graph gives displacement. b) The slope of the displacement - time graph gives velocity.. u = 0; t = 15s; v =?; g = 9.8 ms - Solution: v = u + gt v = (15) v = 147 ms -1 v = u +gh 147 = 0 + (9.8) (h) h = 147 x 147 / x 9.8 (i) h = m (ii) v = 147 ms a) B has greater velocity b) B overtakes A 30 km from the origin after 3 hours. 4. The falling of a body towards the centre of the earth when in space without air resistance is called a free fall. 5. Uniform velocity : If a body cover equal displacements in equal intervals of time, it is called uniform velocity. Average Velocity : It is the ratio of total distance covered by the body to the total time taken. Answer 1. Force = mass x acceleration 1 N = 1 kg x 1 ms - = 1000 g x (100 cm) (1 s - ) 1 N = g cms - 1 g cms - = 1 dyne. 5 1 N = 10 dyne.. It is due to Newton s third law of motion. When a person gets off the boat, he exerts a force on it. He moves forward by pushing the boat backwards. 3. m = 50 x 10-3 ; F =ma = 00 N; v =?; u =0; s = 50 x 10 - m. a = f/m 00 = 50x = ms. v = u + as. 0 = u + (- 4000) (50 x 10 - ) -u =

24 u = 63.4 ms -1. The velocity with which it hits the wooden block is 63.4 ms a) A passenger sitting inside a bus moves forward when it is suddenly stopped. b) Before taking long jump, the athlete runs up a certain distance. 5. Effective length of the simple pendulum = radius of the bob + length of the string. L = l + r Radius of the bob is found using vernier calipers. Answer 3 1. Regular Reflection Irregular Reflection. Sl.No Real Image Virtual Image 1. It is always inverted.. It can be obtained on a screen. It is always erect. It cannot be obtained on a screen. 4

25 3. From the diagram A & A 1 are plane mirrors positions. A is turned through an angleθ. The point of incidence is B. BB 1 is normal to the surface of mirror position A. BC 1 is normal to the surface of mirror position A MBB = DBB = i MBD = i MBD = MBC + C BD = (i + θ) + (r + θ) 1 MBD = i + θ [ Q i = r] 1 1 DBD = MBD - MBD 1 DBD = i + θ - i 1 DBD = θ. 4. a) 360 n = n = 5 images. 360 b) n = 1 30 n = 11 images. 5. The image of an object turns through an angle of 180 o through vertical axis rather than horizontal axis, so that the right side of the image appears as left or vice versa. This process is called lateral inversion. Answer 4 1. a) The sound vibrations of lower frequency have a bass effect. b) The sound vibrations of higher frequency are said to have shrill effect. 5

26 . a) Ultra sonic vibrations are used for welding metals like tungsten. b) For scanning internal parts of the human body. 3. Let time period be T Let f be the frequency. Let f number of waves be produced in 1s. 1 wave is produced in 1 s. f Time taken for one wave is called time period (T) T = 1 or f = 1 f T. 4. Velocity of X = f λ = 500 = 1000 ms -1 Velocity of Y = 400 X = 1000 ms X = X = =.5m Sl.No. Light waves Sound waves 1. Light waves are transverse in nature. Sound waves are longitudinal waves. Light waves have speed 3 x 10 8 m/s Sound waves have speed 340 m/s. 3. Light waves don t require material medium for propogation. Sound waves requires material medium. Answer 5 1. Weight of solid in air = 0.80 kgf mass of solid in air = 0.80 kg Section B m 0.80 Volume of solid = = p = m. 5 Volume of brine solution displaced = x = 1.56 x 10 m mass of brine = v x p = 1.56 x 10 x 300 = kg Upthrust offered = kgf Apprent weight of solid in brine solution = ( ) = = kgf. 6

27 . Relative density of a solid is ratio of density of solid to density of water. 3. a) While floating, the body has no weight and its apparent density is zero. b) The upthrust acts vertically upwards through the centre of buoyancy. c) The weight of the solid acts vertically downward through the centre of gravity. 4. Let the volume of iceberg be v Volume of iceberg above sea = 1 v 6 Volume of iceberg beneath sea = v - 1 v 6 Volume of sea water displaced = 5 v 6 By law of floatation, v iceberg p iceberg g = v water p water g Given, p seawater = 1.17 gcm -3 v iceberg p iceberg = v water p water v p iceberg = 5 6 v p = gcm Lactometer is a specially designed hydrometer which can directly measure densities within the range of 1gcm -3 to 1.045gcm -3. Answer 6 1. Thermostat is a device used for maintaining steady temperature in electrical appliances. It works on the principle of thermal expansion of solids.. Given : L o = 10 cm; L t L o = 0. cm; t = = 570 o c. L t - Lo Coefficient of linear expansion α = Lt o 0. = 10 x o α = 3.5 x 10 / C Coefficient of superficial expansion β = α -5 o = x 3.5 x 10 / C -5 o = 7 x 10 / C γ = 3α = 3 x 3.5 x 10-5 o = 10.5 x 10 / C Trade winds blow from north-east to south-west in the northern hemisphere and from south-east to north-west in the southern hemisphere between 30 o north and 30 o south in both hemispheres. Polar winds blow from 60 o latitude to the poles from it. 7

28 4. The order of frequency of radiant heat is to hertz. 5. Black surfaces absorb heat radiation quickly. But the shining surface do not easily radiate heat. As the heat is trapped inside the cooking utensil in this manner, cooking time is reduced. Answer 7 1. a) A standard unit must be defined without any doubt or ambiguity. b) It should not alter with respect to space and time.. When the zero of the main scale and the zero of the vernier scale do not coincide in a vernier calipers, then it is said to have zero error. Zero correction = Total Reading Zero error. Zero error is positive when the zero of vernier scale is on the right hand side of zero of main scale. Zero error is negative when the zero of the vernier scale is on the left hand side of the zero of main scale. 3. Number of head scale division = 100 Distance moved in the pitch scale pitch = number of rotation given mm = 4 pitch = 0.5 mm pitch least count = number of head scale division 0.5 mm = 100 = mm. 4. l = 1.5 m; g = 9.8 ms - ; T =? g = 4π l T l T=4π g 4 x 3.14 x 3.14 x T =.46 s. T = = a) The plumb line points vertically downward. b) The doors should be closed while taking measurements to avoid air currents. 8

29 Answer 8 1. Conductors are materials that have a large number of free electrons available for conduction under the influence of a potential difference. e.g : All metals are good conductors.. By providing lighting conductors or arrestors mounted at the top of a building. The pointed ends of the conductor leaks charges to the clouds by forming a conducting path. 3. a) When one coulomb of charge is brought from infinity to the given point against the electric field and the work done during the process is one joule then the potential is said to be one volt. b) When 6.5 x electrons flow through a conductor, then the charge is equivalent to one coulomb. 4. Q = 1000c t = 5 x 60 x 60 = seconds. q 1000 I = = = 1 t = 0.055A I = 55 ma. 5(i) Answer 9 1. (i) Variable resistance (ii) inductor (iii) cells in series (iv) fixed resistance 9

30 . a) By heating b) By self induction It is a process of transfer of heat from the hot end to cold end without actual movement of the particles. e.g : non metallic good conductor is graphite. 5. Answer m = 9.1 x kg. v = 6 x 10 7 ms -1 momentum = m x v = 9.1 x x 6 x10 7 = 54.6 x 10-4 = 5.46 x 10-3 kgms -1 30

31 . m = 00 kg s = 10 m, Solution : 80 x 1000 u = 80 kmh = =. ms 3600 v = v = u + as 0 = (.) + (a)(10) a = a = 4.7 ms But, F = ma = 00 x 4.7 Force applied by the brakes F = 4940 N. 3. a) Tangential direction b) Inertia of direction. 4. v - u Acceleration = t 15-0 = 8 r - a = ms Total distance = Area of Δ OAB = 1 x 14 7 x 15 = 105 m N = 1 kgms - 1 J = 1 kgm s 31

32 Physics Paper - 5 Answers Section - A Answer 1 1. When a body does not change its position with respect to the surroundings, the body is said to be at rest. When a body changes its position with respect to the surroundings, then the body is said to be in motion.. Let x 1 and x be the distances covered with speeds 60 kmh -1 and 40 kmh -1 respectively. Let t 1 and t be the corresponding time taken for covering x 1 and x. distance Speed = time distance time = speed t 1 = 30 = 0.5 hour 60 t 30 = = 0.75 hour. 40 (i) Total time of the journey = t 1 + t = = 1.5 hour. total distance (ii) Average speed = = = total time taken = 48 kmh. 3. The body is at rest Total distance travelled = Area of them trapezium OABC = 1 x sum of parallel sides x perpendicular distance. = 1 x (AB + OC) x AD = 1 x (5 + 15) x 40 1 = x 40 0 x 40 s = 800 m. (During uniform velocity, the acceleration of the body is zero). 3

33 Answer 1. a) The passenger sitting in a bus moves backward when the bus suddenly starts moving. b) When coin placed on paper above a water bowl, it falls inside if the paper is pulled fast.. a) To give more time for the ball so that the acceleration is reduced and hence the force of the ball on the hands is also reduced. b) When a vehicle gets into a pit it suffers a large impact due to the mass of the vehicle. The shock absorbers hear the impact by delaying the time taken by the force i.e the weight of the vehicle. 3. m = 10 kg; a = 5 ms - F = ma = 10 x 5 = 50 N. 4. a) Recoil of a gun. b) Motion of a rocket. 5. m 1 = 100 kg; m = 00 kg; d = 10 m; G = 6.7 x Nm kg - G m1m F = d x 10 x 100 x 00 F = 10 x = 1340 x 10-8 = 1.34 x 10 N. Answer 3 1. Pitch = 0.5 mm n =? L.c = mm pitch L.c = number of head scale divisions = n 0.5 n = n = 500 divisions.. The error in a screw gauge due to the wear and tear of the screw is called backlash error. Even though we rotate the tip of the screw, the thimble will not move. To avoid this the screw should be rotated only in one direction. 3. a) 1 ml = 10-6 m 3 b) 1 litre = 1000 cm 3. 33

34 4. a) A seconds pendulum is a simple pendulum whose time period is two seconds. t b) = t = 0. x 4 = 0.8 s. 5. a) The pointer must cover equal distance on the scale b) Wet and hot substances should be avoided on the scale pans. Answer 4 1. a) The image is upright. b) Virtual.. 3. i + r = 90 o i = r i = 45 o, r = 45 o AB = incident ray DB = normal at the point of incidence BC = reflected ray (a) (b) 34

35 4. f = 15cm; object distance = 40cm. r = f i.e r = 30 cm The object is beyond C (i) The image is formed between C and F. (ii) real image. (iii) inverted. (iv) diminished. Section - B Answer 5 1. a) The pressure at a point inside a liquid increases with depth. b) About a given point in a liquid, the pressure is the same in all directions. c) Pressure at a point inside a liquid is directly proportional to the density (with respect to the depth of the liquid).. Pressure due to 1m column of water = hpg 3 = 1 x 10 x = x 10 pa Total pressure at 1 m below the surface of water = atmospheric pressure + pressure due to water column of height 1m. 5 5 = x x 10 5 = x 10 pa. Area of the plate = πr = π x 5 = 5 x 3.14 = 78.5 m Total thrust on the plate = Pressure x Area 5 = (1.111 x 10 ) x = 8.7 x 10 N. 3. When a rubber sucker is pressed against the wall, the air between the sucker and the wall is forced out which creates a vacuum in between. The atmospheric pressure holds the sucker firmly on the wall. 4. a) Mercury is shining and opaque. b) The density of mercury (13600 kgm -3 ) is the largest among all the liquids which helps us to have less height while constructing a barometer. Answer 6 1. Weight of the body in air = 300 gf Weight of the body in water = 80 gf (i) Loss in weight of the body = = 0gf. 35

36 (ii) Upthrust acting on the body = loss of weight of the body. = 0gf.. Sea water gives greater upthrust than the fresh water. Density of the sea water is around 1.04 gcm -3 or 1040 kgm -3 whereas density of fresh water is 1000 kgm -3. Hence it is easier to swim in sea water. 3. Volume of balloon v = 000 m density of helium p = 0.18 kgm density of air He He 3 = 1.9 kgm weight of helium in the balloon = v x p x g = 1000 x 0.18 x g = 180 kgf weight of air displaced = upthrust = v x density of air x g = 000 x 1.9 x g = 580 kgf Resultant upward force = = 400 kgf. The balloon can lift a maximum of 400 kgf of load The sulphuric acid of density 1.5 gcm -3 is used as electrolyte in acid batteries. If it falls below 1.16 gcm -3, the cell is permanently damaged or cannot be discharged. To avoid this situation, a hydrometer of length 10 cm is used which has a short stem and a heavier gravity bulb. 5. Relative density of a substance = x 13.6 = 1000 kgm -3 density of the substance o density of water at 4 c x density in SI unit = 13.6 x 10 kgm 3-3 = 13.6 x 10 kgm density in CGS unit = 13.6 gcm Answer 7 1. a) Nature of the solid b) Initial length of the solid. 36

37 . d = 10 x 10 m; t = 500 C; α = 1.8 x 10 - o -5 o -1 - L o = 10 x 10 m; L =? L - Lo α = Lt o L - 10 x x 10 = 10 x 10 - x 500 C L - 10 x 10 = 1.8 x 10 x10 x 10 x 500 = 9 x x = 0.09 x x = x 10 m or = cm. 3. a) 1000 kgm -3 b) 4 o C. 4. C F-3 a) = 5 9 o Given : F = 86 F C 86-3 = = 6 9 o C = 30 C. o o b) Temperature in C = 100 C Temperature in kelvin scale = = 373 K. 5. a) Air is a poor conductor of heat. So, it hampers the conduction of heat from the room to the outside in winter and vice-versa during summer. b) Radiating power can be increased by making the surface more dull or black. Answer 8 1. distance a) velocity = ; d = 0.5m; t = 0.005s time 0.5 v = velocity of the pulse = 00 ms. 37

38 b) v = fλ Given : f = 300 Hz 00 = 300 x λ 00 λ = 300 λ = 0.67 m.. The distance covered by the disturbance in a particular medium in one second is called its wave velocity. Its S.I unit is ms a) Infrasonics. b) Audible range. c) Ultrasonics. d) Radio waves. 4. (i) They are used for homogenising milk. (ii) They are also used for dissipating fogs on the runways at the airports. 5. Given : number of vibrations = 7 time = 60s 7 frequency = 60-1 f = 1. s or 1. Hz 1 1 Time period = = = 0.83s. f 1. Answer 9 1. Static electricity is a phenomenon in which the charges do not flow. Charging can be done by friction.. In nature, charge is always found in integer multiples of electrons. ie Q = ± ne, where n = 1,,3.. The charge of an electron which is 1.6 x C is the minimum possible charge. 3. The charges are shared by the two bodies. 4. A spark on the fuel may make the truck explode. To avoid this, if any static electricity is generated because of rubbing or conduction, the charges flow directly to the earth as the earth is electrically neutral. 5. Q = ne -c = n x 1.6 x

39 n = 1.6 x Brass. 19 = 1.5 x 10 electrons excess. Answer A primary cell is a one in which chemical energy is directly converted into electrical energy. e.g. : Daniel cell. A secondary cell stores electric energy in the form of chemical energy and when required the chemical energy is converted into electric energy. e.g. : Lead acid cell.. q Current I = t 0 = 0.5 Current I = 10 A. 3. (i) Thickness : As the thickness of a conductor increases, the resistance decreases. (ii) Length : As the length increases, the resistance of the conductor also 39

40 Physics Paper - 6 Answers Section - A Answer 1 1. Yes. If a particle moves from point A to B and back to point A, the displacement is zero. But the distance covered is twice the path length between A and B.. c) An aircraft carrier. The inertia of the body is the measure of its mass. An aircraft carrier is the largest in mass among the examples given. 3. Sl. No. Speed Velocity 1. It is the ratio of distance covered to the time taken by a body without any specified direction.. It is a scalar quantity. It is the ratio of displacement to the time taken by a body in a particular direction. It is a vector quantity. 4. The distance covered by the body is the area of the trapezium OABC 1 = (sum of parallel sides) x (perpendicular distance) 1 = x (AB + OC) x OA 1 = (1 + 16) x 50 5 = 8 x 5 s = 700 m. Answer 1. a) Speed of light x = 3 x 10 8 ms -1 distance travelled by light = speed x time = 3 x 10 8 x 365 x 4 x 60 x 60 = 9.46 x 10 1 km. b) The distance obtained is known as a light year.. L 1 : L = 5 : 36 a) L T L 1 : L = T 1 : T 5 :36 = T 1 : T 5 :6 = T 1 : T T 1 : T = 5 : 6. b) f = 1 T f 1 1 1:f = : = 0. :

41 3. u=0, v = 0ms -1 ; t = s; m=50 x 10-3 kg. r v - u a = t 0 0 = r - a = 10 ms. r r F = ma -3 = 50 x 10 x 10-3 = 500 x 10 N =.5 N. 4. a) Inertia of rest Newton s I law of motion. b) Newton s 3 rd law of motion. Answer 3 1. a) momentum = mass x velocity r -1 p = kg ms. b) moment of a force = Force x perpendicular distance = kg ms - x m. = kgm s -.. pitch = 1 mm PSR = 4 mm; number of Head scale divisions = 100; HSR = 90. pitch L.C. = n HSD 1 mm = 100 L.C. = 0.01 mm. Total Reading = PSR + (HSR x L.C) = 4 mm + (90 x 0.01) = 4.9 mm. 3. First the volume of water in a measuring jar is taken as v 1. Then a piece of iron which can sink is taken and tied to a string. Now it is immersed in water and volume is taken as v. The volume of the solid is (v v 1 ). Now, the object that floats is tied along with the solid iron and immersed in water. Now the volume is noted as v 3. The volume of the object is v 3 -v 1. 41

42 4. a) 1 μm = 10-6 m; b) 1 pico farad = 10-1 farad. c) 1 giga pascal = 10 9 pascal. Answer 4 1. a) Conduction. b) Convection. c) Radiation. d) Radiation.. Sl. No. Heat Temperature a. Heat is measured by a calorimeter. Temperature is a measured by a b. Heat is a form of energy due to random motion of molecules thermometer. Temperature is a measure of degree of hotness or coldness of a body. 3. a) Coefficient of linear expansion : It is equal to the increase in length of a rod of that substance of unit length when its temperature is increased by 1 o C. L t - Lo -1 = C. Lt o b) Coefficient of cubical expansion : It is equal to the ratio of increase in volume of a substance to the original volume at 0 o C per degree rise in temperature. vo -1 γ = v t - K. vot 4. a) Black bodies are good absorbers of heat. If heat is made to fall on a thermometer with a blackened bulb, the rise in temperature is observed. This is called a blackened bulb thermometer. b) Heat radiations can be detected by a thermopile. It consists of a number of bismuth and antimony rods connected in series. Only one end of the junctions are exposed whereas the other end is shielded. The difference in temperature due to heat causes a potential differences and it is detected through a galvanometer. 1. Section - B AB object. A B image. Image is formed at 10.1 cm behind the mirror. Image is virtual and erect. 4

43 . a) b) 3. a) Image is formed at a distance of 100 cm behind the mirror. b) The distance between the person and his images is = 00 cm. 4. a) The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane. b) The angle of incidence is equal to the angle of reflection. i = r. 5. The real image can be obtained on screen where the virtual image cannot be obtained on a screen. Answer 6 1. a) Lateral pressure is the pressure that acts on the sides of the containing vessel. b) The average force acting per unit area by a fluid is called fluid pressure.. a) Pressure of moisture in mercury. b) Vertical height from the sea level. c) Temperature of the atmosphere. 3. a) Aneroid barometer does not contain any liquid. b) It is compact and portable. 43

44 4. Vertical length of water column (h) = 100 cm = 1 m. Density of water (p) = 1000 kgm -3. g = 9.8 ms -. Pressure P = pgh = 1000 x 9.8 x 1 = 9800 pa. 5. Pressure due to height h = hpg = 15 x 1000 x 9.8 = 1.47 x 10 5 pa. Pressure on the ground floor = 1.6 x 10 5 pa. Difference in pressure of water at ground floor and fifth floor = 1.47 x 10 5 pa. Pressure at the 5 th floor = 1.6 x x 10 5 = 0.13 x 10 5 pa = pa. Answer 7 1. Volume of the cylinder = area x length = x 1. V = 1.9 x 10-3 m 3. Mass of cylinder = volume x density = 1.9 x 10-3 x 700 = 13.8 kg. (i) Weight of the solid = 13.8 x 10 = 138. kg wt or = 138. N. Volume of water displaced = volume of solid. = 1.9 x 10-3 m 3. Mass of water displaced = v x p water = 1.9 x 10-3 x 1000 = 1.9 kg. (ii) Upthrust = mg = 1.9 x 10 = 19. N.. a) Floatation of fish. b) Floatation of submarine. 3. a) A bimetallic strip becomes more sensitive to changes in temperature. As the brass expands more than invar, they are used in fire alarm. b) In the balance wheel of a clock, the rim is made of three or more, brass invar bimetallic strips. There is little space left between two strips to allow expansion and contraction. Balance wheel is used in clocks. 44

45 4. L t - Lo = Lt o Increase in length of brass = Increase in length of iron -6-6 L brass t = L Iron 1 10 t -6 Lbrass 1 10 = -6 LIron L brass = L 3 Iron L Iron - L brass = cm L Iron - L Iron = cm 3 1 L Iron = cm 3 L = 6 cm. Iron L brass = L 3 Iron = 6 3 L brass = 4 cm. Answer 8 1. The sound vibrations of lower frequency is called Bass effect. The sound vibrations of higher frequency is called Shrill effect.. Waves that require a material medium for propagation is called material waves e.g.: a) Sound waves b) Water waves. 3. Wavelength ( λ ) = 1 cm = 1 x 10 - Velocity (v) = 0 ms -1 (i) Number of waves in one second = f V = fλ f = v λ f = 0 1 x 10 = 0 x 10 f = 000 Hz. - (ii) Time period (T) = 1 f = = 5 x 10 s. 4. Galton s whistle produces ultrasonic waves. Dogs are specially trained to respond to these whistles. 45

46 5. Answer 9 1. a) For detection of charges. b) For identification of kind of charges.. a) Electric conduction is the phenomenon where there is a flow of electrons due to potential difference. b) Electrostatic induction is a phenomenon due to which an insulated uncharged conductor gets electrically charged when held near a charged body. 3. Surface density of charge is the quantity of charge per unit area. Its unit is cm When a charged cloud discharges lightning, due to the pointed ends of a conductor, the charged particles flow through a conductor. Lightning arrestors are used for the safety of buildings to avoid lightning. 5. a) b) Answer (a)electric potential is the amount of work done (energy spent) in moving a unit positive charge from infinity to a given point in an electric field. 46

47 (b)electric potential difference is the amount of work done in moving a unit positive charge from one point to another in an electric field.. Q = 50 C ; W = 100 J ; work done Potential = charge 100J = 50C = V 3. Primary cell : A cell in which chemical energy is directly converted into electrical energy is called primary cell. It cannot be recharged. e.g. : Leclanche cell, Daniel cell. Secondary cell : Secondary cell is a one which chemical reaction is reversible. It can be recharged. e.g: Lead acid accumulator. Ni Fe accumulator. 4. a) Magnetic field lines are directed from the N-pole towards S-pole of a magnet. b) They behave like stretched elastic rubber strings. c) The tangent drawn at any point on a field line shows the direction of magnetic 47

48 Physics Paper - 7 Answers Section - A Answer 1 1.a) Measurement is the process of comparing the unknown magnitude of the given physical quantity with the known standard quantity of the same kind. c) A unit is standard quantity of constant magnitude for measurement. d) The number of times the unit of a given physical quantity is its magnitude..a) 10 - m b) kg. 3.a) The least count of a vernier callipers is the difference between one main scale division and one vernier scale division. b) Pitch of a screw gauge is the ratio of the distance moved on the pitch scale to the number of rotations given to the head scale. 4. The effective length of a simple pendulum is taken from the radius of the bob to the point from where it is suspended. The measurement of the string is measured by a meterscale and the radius of the bob is measured using a vernier callipers. 5. The best fit line is drawn by making the line pass through the maximum number of points or it passes closest to the maximum number of points which appear on both sides of the line. Answer 1. displacement a) velocity = time 100 km = hour -1 v = 50 kmh. -1 b) velocity in ms = 50 x x = 36-1 = 13.9 ms.. 48

49 3. a) The position time graph of a body at rest. b) The velocity time graph of a body moving with uniform velocity. 4. Velocity = 90 kmh -1. = 90 x = 5 ms. (i) distance = velocity x time = 5 x 8 = 00 m or 0. km. (ii) acceleration in ms - = velocity time = 5 8 = 3.15 ms a) The slope of a distance time graph give the velocity of the body. b) The area of the velocity time graph gives the distance travelled by the body. Answer 3 1. Every body continues to be in a state of rest or uniform motion along a straight line until it is acted upon by an external force. Inertia is the tendency of the body to be at rest or uniform motion along a straight line.. Given m = 00 kg; u = 80 kmh -1 = 80 x 5 18 =. ms-1 ; v = 0; s = 10 m. Solution : v = u +as 0 = (.) + (a) (10) = 0a Retardation a = = ms Retarding force F = ma = 00 x 4.7 F = 4940 N. 1. The force with which a body is attracted towards the centre of the earth is called its weight. The S.I unit of weight is N or Newton.. a) Electrostatic force b) Gravitational force. 49

50 3. -1 velocity = 50 kmh = -1 = 13.9 ms. 50 x = 50 x 60 x Answer 4 1. a) Whenever any pressure is applied on any part of the boundary of a confined fluid, it is equally transmitted in all directions and it always acts at right angles to the surface of the vessel. b) 1. Hydraulic press. Hydraulic brakes.. a) The atmosphere pressure decreases. b) The fluid pressure increases with depth. 3. Pressure P = hpg Given p = pa, h = 1 m; g = 9.8 ms -. P =? = p x 1 x p = p = kgm. 4. a) The ratio of density of a substance to the density of water at 4 o C is known as relative density of a substance. b) Relative density has no unit. c) CGS unit of force is dyne. Answer 5 1. Section - B Sl.No. Heat energy Temperature 1 Heat is a form of energy which causes the sensation of hotness or coldness. Temperature is the degree of hotness or coldness of a substance.. It is measured in Joule. It is measured in o Celsius or o Fahrenheit or Kelvin.. a) The liquid should have very low specific heat capacity. b) It should not stick to the sides of the walls of the thermometer. 50

51 3. Absolute zero is the lowest temperature at which the molecular movement of matter stops. There is no negative scale in the kelvin scale. 4. Given : o o x F = - x C F - 3 C = 9 5 x - 3 x = ( x - 3) = - 9x 5 x = - 9x 14 x = x = 14 o = F. i.e o F or o C are equal. 5. a) K -1 or o C -1. b) Bimetallic strip is a combination of two plates of different materials reverted together at a number of points. Answer 6 1. The water in cells of human beings freezes (in the exposed parts) because of the anomalous expansion of water during very cold regions. This causes bursting open of cells.. Igloo, the houses of Eskimos, are made out of snow. As the snow contains large quantities of trapped air, it acts as an insulator. Hence their bodies are warm. 3. During day, the land gets warmed faster than the sea in coastal regions. Due to this, the warmer and lighter air moves up. To replace this, breeze which is cooler in temperature flows from the sea. This is called sea breeze. Similarly, land breezes are from the land into the sea as land cools faster than sea water as the specific heat. Capacity of land is five times less than that. Both land and sea breezes are caused by the method of convection of heat. 4. Reflecting power of a body is the ratio of quantity of heat reflected by the body in one second to the quantity of heat received by the body in one second. Absorbing power of a body is the quantity of heat absorbed by the body in one second to the quantity of heat falling on it in one second. 5. Thermopile is used for detecting heat radiations. 51

52 Answer 7 1. Image formed in a plane mirror is (i) always virtual. (ii) The image is as far behind the mirror as the object is in front of it.. The principle of a periscope is based on the reflection of light at the two parallel plane mirrors facing each other and each kept inclined an angle of 45 o with the vertical. Uses : (i) It is used by the submarines to keep vigil on the other ship s movement in sea. (ii) It is used in bunkers to view the movements of others on the ground. 3. a) Pole : The geometric centre of the spherical surface of the mirror is called the pole. b) Aperture: The area of the reflecting surface available for reflection in a mirror. c) Principal focus : Principal focus is a point on the principle axis, where a beam of light parallel to the principal axis, after reflection either appears to converge or diverge from it. 4. a) b) A 1 B 1 is the inverted real image formed at C which is of the same size. A 1 B 1 is the virtual erect image formed behind the mirror. Answer 8 1. Frequency f = 00 x 10 3 Hz. Time period T = 1 f 5

53 1 = 00 x 10-6 = 5μs or 5 x 10 s. 3. Distance = velocity x time = 345 x 3 = 1035 m Hz to 0000 Hz. Answer If the energy transfer is along the plane of propagation, then it is said to be a longitudinal wave. e.g Sound Waves. 5. (i) amplitude = m. (ii) Time period T = s. (iii) frequency f = 1 T = 1-1 = 0.5 s. 53

54 Principle : The induced changes from the sharp points of the lightning conductor, attracts the heavy charges from the cloud which is lightning.. Accumulators or secondary cells are the source of electric current as a result of chemical reaction and they can be recharged after use. e.g : Lead acid accumulator. 3. a) Cell. b) Battery. c) A.C. source. d) A closed plug key. e) Variable resistance. f) Rheostat. 4. a) Resistance. Answer work done Potential difference = charge 0 = 3 = 6.66 V.. a) the resistance is also doubled. b) the resistance becomes one fourth. c) the resistance also increases. 3. a) The north and the south poles exist in pairs. b) Like poles repel and unlike poles attract. 4. No. The magnetic field lines never intersect because at the point of insection when a magnetic needle is placed the north pole of the needle will point in two directions which is not possible. 5. No. It is not possible to isolate the poles of a 54

55 Physics Paper - 8 Answers Section - A Answer 1 1. a) Total distance travelled = = 100 km. b) Displacement is zero.. A body is said to have uniform acceleration if its velocity changes equally in equal intervals of time however small the intervals may be. Its unit is ms a) time taken to reach the highest point = t second. b) At the highest point, the velocity is zero. 4. a) Total distance travelled = = 90 m. distance travelled b) velocity = time taken from O to A = 45 = 7.5 ms-1. 6 c) acceleration is zero. d) retardation is zero. Answer 1. a) 10 5 s. b) m.. Value of 1 Main scale division = 1 cm = 0.05 cm. 0 Number of vernier divisions = 5 Least Count = 1MSD n = 0.05 cm 5 = 0.00 cm. 3. v 1 = 0.0ml; v = 4. ml volume of the coin = 4. ml. 1 cm 3 = 10-6 m 3 4. CC = 4. x 10-6 m A seconds pendulum is a simple pendulum, whose time period is two seconds. 5. T 1 :T = :1 l T l 1 :l = T 1 : T l 1 :l = :1 55

56 1 The ratio of their lengths l Answer 3 1. = 4:1. When V 1 = 0.3, I 1 = 0.6v and when V = 1.1, I =.V V - V I - I Slope = = = Slope = Slope = V = 0.5 I 0.5 Ω is the resistance of the conductor.. When a person sitting on a swing stands up, the effective length of the swing decreases. We know that when length decreases, the time period also decreases since l T. 3. a) Momentum vector. b) energy - scalar. c) mass - scalar. d) velocity - vector. e) work done - scalar. f) pressure - scalar x km h = = 7 x = 0 ms 60 x Speed in ms = 0 ms. 56

57 Answer L = 1 m; L = x 10 m = m. o o t = 80 c L t - Lo α = Lt o = 80 x α =.03 x 10 k.. a) 1 J = 10 7 erg. b) 1 calorie = 4. J 3. a) Thermal conduction. b) Convection. c) Radiation. t 4. Hot air is less dense than cool air. Hence the hot air moves up and the cool air from the air conditioner replaces the hot air. Because of this reason, air conditioners are installed near the ceiling. 5. Green house is an enclosure with a glass ceiling where plants are grown. The interior is warmed up by the smaller wavelengths of sun s rays during day. At night, the radiant heat given by the interior of the house is longer in wave length and the temperature is greater. So, it cannot leave the green house making it conducive for the growth of the plants. Section B Answer 5 1. If the object is moved 50 cm away, the image is now formed 150 cm away from the mirror M. So, now from the previous position, the new image is moved 100 cm away from the previous position.. (i) The incident ray, reflected ray and the normal at the point of incidence all lie on the same plane. (ii) The angle of incidence is equal to the angle of reflection. i = r 3. a) infinite number of images, 360 b) n = - 1 θ 360 n = n = 3. Number of images formed = 3. 57

58 4. a) Real image. b) Image is enlarged. Answer 6 1. (i) A person sitting in a moving bus tends to go forward when the bus suddenly stops. (ii) A bowler runs up a certain distance before delivering a ball.. m = 100 x 10-3 kg; u = 100 ms -1 ; v = 150 ms -1 ; t = 5s. momentum = mass x velocity. a) Initial momentum = 100x 10-3 x 100 = x 10-3 = 10 kg ms -1 b) Final momentum = 100 x 10-3 x 150 = 15 kg ms -1 c) Rate of change in momentum = m(v - u) t = mv - mu t = = 1 kg ms -1. d) Acceleration of the ball = v - u t = = = 10 ms -. e) Force F = m x a. = 100 x 10-3 x 10 = 1 N. 3. a) Recoil of a gun. b) A swimmer pushes water to leap forward. 4. w = mg = 10 x 9.8 = 98 N. 58

59 Answer 7 1. a) depth of liquid from the free surface. b) density of the liquid.. Volume of the cube = x x = 8 cm 3 density of the cube = 8 gcm -3 mass of the cube = volume x density = 8 cm 3 x 8 gcm -3 = 64 g. weight of the cube = 64 gf (downwards) upthrust on cube = weight of liquid displaced. = volume of cube x density of liquid x g. = 8 x 1 x g upthrust = 8 gf (upwards) Tension on the thread = Total downward force = weight of the cube upthrust on the cube = 64 8 T = 56 gf. 3. The density of a substance is the ratio of its mass per unit volume. The relative density of a substance is the ratio of the density of the substance to the density of the substance to the density of water at 4 o c. 4. Hydrometer is a device used for finding the relative density of a liquid. It works on the principle of floatation. Principle of floatation : The weight of a floating body is equal to the weight of the liquid displaced by its submerged part. Answer 8: 1. a) sound waves - mechanical waves. b) radio waves - non mechanical waves. c) sea waves - mechanical waves. d) seismic waves - non mechanical waves. e) micro waves - non mechanical waves. f) heat waves - non mechanical waves.. a) Pressure. b) Humidity. c) Temperature. 3. a) velocity of the pulse = displacement time = v = 00 ms

60 b) wave length = velocity frequency = λ = 0.5 m. 4. a) 0 Hz 0,000 Hz. b) Sonographic Navigation and Ranging. Answer 9 1. The electrons in the outermost orbit are called valence electrons. In a solid, the valence electrons leave their atoms and freely move inside it. These electrons are called free electrons.. a) b) 3. When two charged bodies are brought closer, due to ionization of air between the two bodies, a spark appears with a chit chit sound. This is called sparking. 4. According to quantum nature of charge, charge it always present as an integer multiple of electronic charge e. ie Q = ± ne. where n = 1,,3,4 from this, we understand that there can never be a fraction of e. 5. The divergence increases. This is due to the addition of more positive charge to the already existing positive charge of the gold leaves. Since they acquire more charge of the same kind they diverge further. Answer The rheostat is used in an electrical circuit for varying current. 60

61 . ne Current I= t n mA= = n n = = n = electrons. 3. (i) Electric current. (ii) charge. (iii) resistance. (iv) potential difference. 4. a) The points located slightly inside a bar magnet where most of the magnetic power is concentrated is called the poles of a magnet. b) Magnetic axis is an imaginary line joining the magnetic north and south poles of a bar magnet. c) The distance between the magnetic north and the magnetic south pole of a bar magnet is called its effective length. 61

62 Physics Paper - 9 Answers Section - A Answer gms -1 1 = 1 x kg x 1 x s = 1 x 10-3 kg ms -1. 1gms -1 = 1 x 10-3 Ns. x = 1 x a) Candela. b) mole minutes = 60 = 6 x 10 1 order of magnitude = = 10 number of second in an hour = 3600 = 3.6 x 10 3 order of magnitude = value of 1 main scale division (MSR) = 1 cm = 0.1 cm 10 number of vernier scale divisions (n) = 10 Least Count = 0.1 = 0.01 cm. 10 Length = MSR + (CVD x LC) = 5 cm + ( ) l = 5.07 cm. i.e., l = 5.07 x 10 - cm. diameter = 1. cm + (7 x 0.01) d = 1.7 cm = 1.7 x 10 - m. πd volume of a solid cylinder = 4 l Answer 1. Force, momentum. - (1.7 x 10 ) = 3.14 x 4 = 6.4 x 10-6 m 3. x (5.07 x 10 - ). A virtual erect image is formed when the object is between the pole and the principal focus of a concave mirror. AB object. A 1 B 1 image behind the mirror M. 6

63 3. Every body in this universe every other body with a force which is proportional to the product of their masses and inversely proportional to the square of the distance between them. r Mm i.e. F r r GMm F = r Fr G = Mm SI unit of universal gravitation constant is Nm Kg No. The value of g decreases with altitude Bangalore will have slightly less value of g than Chennai because of its altitude. 5. At 4 o C. Answer 3 1. Negative acceleration is called retardation. Its unit is ms displacement = diameter = x radius. = x = 000 m. Distance covered by the car = 1 x πr = πr = 3.14 x 1000 d = 3140 m. 63

64 4. The ball is thrown vertically up. The under goes uniform retardation. 5. u = 0; t = T 3 1 s = ut + gt h = 1 gt = 1 gt T = h g 1 T h = x g x 3 1 = x T g x 9 g 1 h = x x 9 g 1 g h = x x 9 g The height of ball = h T m. after second 9 3 Answer 4 1. d = 5 km = 5000 m p seawater = 1030 kgm -3. g = 9.8 ms -. Pressure P = pgd = 1030 x 9.8 x 5000 P = x 10 7 pa.. Let V be the volume of the block. If 0%, ie 0 x V = 0.V is above water. 100 i.e. 0.8 V of the block is under water. mass of water displaced = 0.8 v x 1000 = 800 v weight of the floating body = weight of water displaced. 64

65 p 1 v = 800v. Density of the block p 1 = 800 kg m Pascal s law. 4. Newton or N. 5. The volume of raft v = mass 50 = density 600 = m3. The maximum water it can displace = volume x density of water. = x 1000 = 83 kg. Section - B Answer 5 1. Force F = m.a; v = 0; u = 80 kmh -1 = 80 x t = 10s; m = 150 kg. where a = v - u t = r 10 - a = -.66 ms Force = 150 x (-.66) = -399 N. ie force required to stop the vehicle is 399 N. = 6.66 ms-1. Nuclear force, electrostatic force, gravitational force. 3. Distance travelled s = Area of the trapezium OABC = 1 x sum of parallel sides x perpendicular distance. 65

66 Distance travelled s = 50 m. = 1 x (0 + 5) x 0 4. L = 50 cm = 0.5 m; g = 10 ms - g = 4π L T T = 4π L g = 4 x (3.14) x T = Time period T = 1.4 s. Answer 6 1. a) Temperature of the atmosphere, b) Presence of moisture in the barometric liquid.. At the ground level, the fountain pen contains some ink in their tube along with air at atmospheric pressure. When it is taken to higher altitudes, the pressure outside falls. Consequently, the air within the tube exerts pressure and forces the fountain pen to leak ink. 3. meta centre is the point where the vertical line passing through the new centre of buoyancy meets the original line passing through the centre of gravity and original centre of buoyancy. (a) meta centre is above the centre of gravity in the stable equilibrium. (b) meta centre lies beneath the centre of gravity in unstable equilibrium. (c) At neutral equilibrium the centre of gravity of the body and the meta-centre coincide. 4. a) Lactometer. b) Acid Battery hydrometer. Answer 7 1. (i) Water has the highest specific heat capacity. (ii) It sticks to the glass surface.. a) Temperature in Kelvin = 73 + t = = 73 K. F - 3 C b) = 9 5 F = 9 5 = (-40 x 9) + 3 = = -38 o F. 3. L o = 10 cm = 10 x 10 - m; t = = 570 o C; L - L o = 0. cm = 0. x 10 - m. 66

67 Solution: L - Lo Linear coefficienct of expansion α = Lt o 0. x 10 - = 10 x 10 - x 570 Superficial coefficient of expansion β = α Coefficient of cubical expansion γ = 3α -5 o α = 3.5 x 10 / C. = x 3.5 x o β = 7 x 10 / C. = 3 x 3.5 x 10-5 o γ = 1.05 x 10-4/ C. 4. Thermostat is a device to maintain steady temperature in various electrical appliances. Answer 8 1. Lateral inversion is a phenomenon in which the image of an object turns through an angle of 180 o through vertical axis so that the right side of image appears as left or vice versa.. number of images = 360 n - 1 = 360 n - 1 = 10-1 number of images = a) Plane mirror periscope. b) Convex mirror rear view mirror in automobiles. c) Concave mirror - shaving glass

68 Characteristics of image : 1. Image is real.. Highly enlarged. Answer 9 1. a) Elasticity. b) Density.. (i) Distance between two consecutive crests = wavelength λ = 45 cm. 1 (i) frequency = Time period (ii) frequency = f = 4 s -1 Time period T = 1 f = 1 4 T = 0.5 s. (iii) Wave velocity = v = fλ = 4 x 45 = 180 cms Waves that need a material medium for propagation are called elastic waves or mechanical waves. e.g.: sound waves. 4. Earth is considered to be at zero potential. The reason behind this is a fact that whatever may be the amount of electrons removed or taken from it, it will not alter its state since it has huge store of electrons. 5. Given Q = 100C; w = 5J; v =? work done (W) potential v = charge (Q) 5 = 100 = 0.05 v. 68

69 Answer Series combinations of resistances. R s = + = 4 Ω. 4 Ω is the value of resistance in series combination. 3. (i) Ferromagnetic substances e.g Iron. (ii) Diamagnetic substances e.g Gold. (iii) Para magnetic substances e.g. platinum. 4. a) Isogonic line is a line that joins all the places having same angle of declination. b) Agonic line joins all the places on earth having zero 69

70 Answer 1 1. a) 1 N = 10 5 dyne. 1 dyne = 10-5 N ie 100 dyne = 10-3 N. Physics Paper - 10 Answers Section - A b) 1 J = 10 7 erg 1 erg = 10-7 J 30 erg = 3 x 10-6 J.. a) velocity of light = 3 x 10 8 ms -1 1 kmh -1 = ms-1 = 5 ms ms -1 = 18 kmh x 10 8 ms -1 = 3 x 10 8 x 18 5 = 1.08 x 10 9 kmh -1. b) velocity of sound = 330 x 18 5 = 1188 kmh a) J kg -1 k -1 b) 3 ma. c) 100 ms -1 d) 100 Ns. 4. a) Least Count (L.C) = value of 1 main scale division (MSD) number of vernier scale division (n) 1 MSD = 1 cm ; 0 n = 10 1 MSD = 0.05 cm. L.C. = L.C. = cm. b) Upper jaws of the vernier calipers are used for finding the inner diameter of a hollow cylinder. Answer 1. a) Time period T = s. frequency f = 1 T f = 0.5 s

71 b) L = 0.5 m; T = 0 = 1s. 0 Acceleration due to gravity g = 4π c) Tension is just a reactionary force. Tension T = 1000 N. L T = 4 x (3.14) x = x 3.14 x 3.14 = 19.7 ms -.. a) It does not overflow. The weight of ice is equal to the height of water displaced. So, when the ice cubes melts, the volume of water produced is equal to the volume of water displaced by the ice cube. b) The pressure at the bottom of a reservoir will be enormous due to its depth. To withstand such pressure, the bottom of it is built thick. c) More than 0,000 Hz. Answer 3 1. a) Wavelength of a radiation is independent of temperature. b) accuracy of measurement is very high.. Yes. The body has centripetal acceleration. 3. The steering wheel can also be considered as an accelerator since it changes the direction of velocity of an automobile. 4. Both vehicles have the same acceleration. Change of velocity Acceleration of the car = time interval 30-5 = = 1 ms - 5 Acceleration of the bicycle = 5-0 = 1 ms The area under the acceleration time graph of a body undergoing uniform acceleration gives the change in velocity of the body. Answer 4 1. a) Sphygmomanometer. b) x 10 5 pa.. Let S 1, S and S 3 be the distances travelled during the time intervals t 1, t and t 3 respectively. For distance S 1, Speed = 30 kmh -1 = 30 x 5 = 8.33 ms

72 time t 1 = 5 minutes = 5 x 60 = 300 second. distance travelled S 1 = 300 x 8.33 = 500 m. For distance S, speed = 60 kmh -1 = 60 x 5 = ms-1 18 time t = 10 minutes = 600 second. distance travelled S = 600 x = m. For distance S 3, speed = 0 kmh -1 = 0 x 5 = 5.55 ms-1 18 time t 3 = 3 minutes = 180 s. distance travelled S 3 = 5.55 x 180 = 1000 m. Total distance travelled S = S 1 + S + S 3 = = m. total distance Average Speed = total time taken = = = 1.5 ms Saw dust is a bad conductor of heat. When ice is covered with saw dust, it is protected from the surrounding so that it does not melt. 4. The coefficient of cubical expansion is the ratio of increase in volume to its volume at zero degree Celsius per degree rise in temperature. Answer 5 1. a) Strongest force nuclear force. b) Weakest force gravitational force. Section B. a) The slippery wet surface does not give enough reaction for the person to walk. b) Motion in one dimension motion along a straight line Motion in two dimension motion of a body in a plane Motion in three dimension motion of a body in space. 3. u =0, v = 500 ms -1 m = 0.1 kg, s = 1m, F =? Applying v = u + as 500 = 0 + x a x 1 a = = 1.5 x 10 5 ms - 7

73 Average force exerted on the bullet = F = ma = 0.1 x 10-3 x 1.5 x 10 5 = 1.5 N. 4. It is opposite to the direction of the body s weight. Answer 6 1. (i) Planet earth revolving around the sun. (ii) Motion of a simple pendulum.. Sound needs a material medium like air for propagation. Moon does not have atmosphere. Hence two astronauts on the surface of the moon cannot hear each other. 3. velocity = distance time distance time = velocity 3 10 x 10 = = 1.9s a) γ is the ratio of specific heat capacity of a gas at constant pressure (C p ) to its specific heat capacity (C v ) at constant volume. Cp γ = Cv b) It has no unit. c) Its value is 1.41 in air. 5. Speed of sound increases with more moisture (humidity) in air. Answer 7 1. a) Global warming is the increase in average temperature of the earth s surface due to the increase in green house gases. b) (i) There will be a sudden rise in sea level on the coastal regions. (ii) It causes unpredictable weather changes resulting in natural calamites. c) Carbon dioixide, Chlora fluoro carbons.. a) Thermal conduction. b) Thermal convection. 3. Boiling point of water in o C = 100 o C The formula is C = F F - 3 = = F The boiling point of water in o F = 1 o F. 4. Radiation. 73

74 Answer 8 1. O object; I 1, I images; M 1, M plane mirrors at 45 o ; A,B - windows. (i) (ii) (iii) Image is real. Image is inverted. Enlarged. AB Object; A 1 B 1 image. 3. The phenomenon of light travelling in straight lines is called rectilinear propagation of light. 4. Real image : It is an image that can be obtained on a screen. Virtual image : It is an image that cannot be obtained on a screen but can only be seen. Answer 9 1. a) 1 m = o A b) 1m = fermi c) 1pf = 10-1 F d) 1 giga pascal = 10 9 pa. 74

75 . a) The electrons in the outermost orbits are known as valence electrons. b) A positive ion is called a cation. c) 1.6 x C. 3. a) The divergence of the gold leaves decreases. b) Negative charge E Cell. K Plug key. A Ammeter. V Voltmeter. R 1,R Resistances Rh Rheostat. Answer The unit of potential difference is volt. The potential difference between two points is 1 volt if 1 joule of work is done to transfer 1 coulomb of charge from one point to another.. When the length of m wire doubles to 4 m, its resistance also becomes doubled. Hence its resistance is 10 Ω. 3. (i) The tangent drawn at any point on a field line gives the direction of the magnetic field at that point. 75

76 (ii) The magnetic field lines never intersect one another. 4. Magnetic field in a vector. 5. a) b) c) Magnetic 76