Work, power and energy HOLIDAY HOME WORK PHYSICS CLASS10 1) When does a force do work? 2) Name and define a physical quantity which has unit kgm 2/ s 2? 3) Give factors on which work depends? 4) Write an expression for work in the following cases A) When force and displacement are in same direction B) When force and displacement are inclined to each other at an angle 5) State the condition when the work done by a force is positive and maximum? Give examples 6) A body acted upon by force. State two conditions when the work done is zero. 7) State the condition when the work done by a force is negative? Give examples 8) A man carrying a load on his head moving on a horizontal surface does no work explain? 9) A body is falling freely and another body is thrown up compare the work done by gravitational force on both bodies 10) A satellite revolves around the earth in a circular orbit. What is the work done by the force of gravity. 11) What is the work done by the moon when it revolves around the earth? 12) The work done by a fielder when he takes a catch in a cricket match is negative. Explain. 13) Who does more work: a man with load walking along a straight road or a man with same load climbing up stairs? give reason 14) What is the work done by force of gravity when a person comes down a certain height using stairs, lift or a slope? give reason 15) Name and define SI unit of work? 16) Name and define CGS unit of work? 17) Obtain the relation between SI and CGS unit of work? 18) Define energy and state its SI unit? 19) A) 1kWh= J b) 1eV= J 20) Name and define a physical quantity which a unit J/s? 21) Give the unit of power which is used in mechanical engineering and give its relation to SI unit 22) State and define Si unit of power 23) Differentiate between the following : a) Work and power(3 points) b) Power and energy
24) State the angle between force and displacement to obtain a) maximum work b) minimum work 25) What is the work done on the body by a force a) Body does not move b) body moves perpendicular to direction of force c) body moves along direction of force d) Body moves opposite to direction of force 26) State the amount of work done by an object when it moves in a circular path for one complete rotation.give reason. 27) Explain the motion of a planet around the sun in a circular path. 28) 1J= cal. 1cal= J. 1J= erg. 1HP= W 29) What is the difference between the units KW and KWh? 30) What is the work done by the moon when it revolves around the earth? 31) Give expression for the work done by gravitational force on a body of mass m climbing to height h by stairs would there be any difference in he work done on the boy if he climbs to same height using lift or slope? 32) Define the following units A) KWh B) ev c) Calorie 32) Define kinetic energy and state its SI unit 33) Derive the relation for calculating the kinetic energy 34) State an expression relating KE and P 35) Can a body possess energy without momentum? If so, give a reason for your answer 36) Can a body possess momentum without energy? If so, give a reason for your answer 37) State work energy theorem 38) Derive work energy theorem mathematically 39) When a stone placed at a height dropped on nail fixed in wooden piece begins to penetrate, give reason? 40) When an arrow is released from a stretched bow it flies away, from where does it get the energy to move? 41) On releasing a compressed spring the ball placed on it flies away,give reason?
42) State energy conversion in the following Electric generator, Electric motor Termocouple, Microphone Loudspeaker, Battery while charging Battery in electric circuit, Kerosene lamp Burning candle, Electric Bulb, Photovoltaic cell Fire crackers Lead accumulator, burning of Wood Steam engine, Toaster, oven, geyser Electromagnet, Photosynthesis Respiration, Water falls A car going up a hill, Washing machine Electric bell, Solar cell Wind mill, Nuclear reactor Rubbing hands, Throwing body into air Hydroelectric power station 43) Differentiate between renewable and non renewable sources of energy 44) Give any two measures for judicious use of energy 45) What is a solar cell? Give its disadvantages 46) What are the advantages and limitations of using wind mills? 47) What are the advantages and limitations of using hydro energy? 48) What is nuclear energy? Give its advantages and limitations 49) What is the reaction taking place in nuclear reactor and what is the source of energy in this reaction? 50) State law of conservation of energy 51) Show that the total sum of mechanical energy remains constant in the case of freely falling body 52) Draw a diagram to show energy changes in an oscillating simple pendulum.indicate in your diagram how the total mechanical energy init remains constant during oscillation 53) What do you mean by energy degradation? Give two examples 54) A body of mass m is moving with velocity v what will be the ratio of initial KE to final KE when mass of body is doubled and velocity is halved? Force 1) Define force
2) What are contact forces? Give examples 3) State the direction of restoring force in pendulum when it is in a) at rest position b) at extreme position? Draw diagrams to illustrate your answer 4) When a spring is stretched, what force will come into play? State its direction? How is this force set up? Name a device which works on this principle? Draw diagram to show its direction 5) Two bodies A and B collide with each other,f Ab is the force exerted by A on B and F BA is the force exerted on by B on A. Give relation between A and B in respect to their magnitude and direction? 6) What is the effect of force on a) rigid body b) non-rigid body 7) What are non contact forces? Give examples 8) Which property is common to non contact forces 9) State Newton s first law of motion 10) State Newton s second law of motion,express it mathematically 11) Under what conditions does Newton s second law can be expressed as F=ma? 12) Name and define a physical quantity which is conserved when a rocket moves up? 13) Draw graphs for acceleration against force and acceleration against mass 14) Name a physical quantity which has unit Ns? 15) Give SI units of the following a) momentum b) rate of change of momentum 16) Define the SI unit of force 17) Obtain the relation between SI and CGS of force 18) Define 1Kgf and 1gf 19) 1N= dyne,1kgf= N 20) 1N= gf, 1kgf= gf, 1gf= dyne 21) Name and Define the physical quantity which has unit Nm 22) On what factors does the torque depend? 23) Which moments are assigned positive and negative conventionally? 24) Why is it easy to open a door by applying small force at the handle? 25) Why is the upper circular stone of a hand flour grinder provided with a handle near its rim? 26) Why a spanner provided with a long handle? 27) What is a couple? Give examples of couple in daily life 28) Define moment of a couple 29) When is a body is said be in equilibrium? 30) Define static equilibrium. Give examples 31) Define dynamic equilibrium. Give examples 32) Give conditions for body to be in equilibrium 33) State principle of moments. Name a device which works on this principle? 34) What is center of gravity? 35) Does the center of gravity remain the same if the body is deformed? Give a reason for your answer 36) Is it necessary that CG always lies within the body? Give example 37) State where does CG lie in the following a) rod b) hollow sphere C) cylinder d) solid and hollow cone e) triangular lamina f) rectangle, square, parallogram
38) When a ship is loaded, the lowest deck is loaded first, why? 39) In a double Decker bus the passengers in upper deck are advised not to stand, why? 40) A uniform circular motion is said to be an accelerated motion. Explain it. 41) Differentiate between uniform linear motions and uniform circular motion 42) Name and define the force required for circular motion? State its direction 43) Name and define force experienced only in rotatory frame of reference? State its direction 44) Differentiate between centrifugal and centripetal forces 45) State from where does the body obtain necessary centripetal force in following cases a) Moon moving around earth b) Planet revolving around sun c) Electron moving around nucleus in an atom d) A stone to a string whirled in circular path 46) A small pebble is placed near the periphery of a circular disc which is rotating about its axis a) What will you observe when you are standing outside the disc? Explain it. b) What will you observe when your standing at the center of disc? Explain it. 47) On what factor does CG depends. 48) When a body is placed on a table top, it exerts a force equal to its weight down wards on the table top but does not move or fall. Name the force exerted by the table top. What is the direction of force? Radioactivity 1) Define work function and state and define its SI unit 2) Define thermionic emission 3) Define electron emission. Name two ways by which electron emission possible. 4) Name the unit in which work function is measured. How it is related to its S.I unit. 5) Give two requisites of an electron emitter with reason. 6) State the principle of Cathode ray tube. 7) Which of the radioactive radiations have zero mass and similar to cathode rays. 8) A radioactive substance is oxidized. What changes would you expect to take place in nucleus and why? 9) Why are the materials of low work function preferred as thermionic emitters? 10) What is meant by radioactivity? 11) Give two factors on which thermionic emission depens. 12) What are radioactive isotopes? Give two uses. 13) Draw a diagram of hot cathode ray tube.give two uses. 14) Mention any two differences between chemical energy and Nuclear energy. 15) Name the three parts of hot cathode ray tube. Mention the principle of these parts. 16) Name a device which converts electric signal to visual signal 17) In a cathode ray tube state 1) the purpose of covering cathode by thorium and carbon 2) the purpose of fluorescent screen
18) Which of the radioactive radiations 1) can cause severe genetical disorders 2) are deflected by electric field 19) A radioactive nucleus undergoes a series of decays according to the sequence X----β---- X 1 ----α----x 2 ---α X 3.If the mass number and atomic number of X 3 are 172and 69 respectively.what is the atomic number and mass number of X. 20 ) What is meant by Nuclear waste. Suggest one way safe disposal of Nuclear waste. 21) What are background radiations? 22) Name two internal sources and external sources of background radiations 23) Name a common device where a hot cathode ray tube is used 24) Give two precautions in handling radioactive substances. 25) Mention safe methods of establishing nuclear power plants. ****************