SRI LANKAN PHYSICS OLYMPIAD MULTIPLE CHOICE TEST 30 QUESTIONS ONE HOUR AND 15 MINUTES

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1 SRI LANKAN PHYSICS OLYMPIAD - 5 MULTIPLE CHOICE TEST QUESTIONS ONE HOUR AND 5 MINUTES INSTRUCTIONS This test contains ultiple choice questions. Your answer to each question ust be arked on the answer sheet that accopanies the test. Only the circles preceded by nubers through are to be used on the answer sheet. Select the single answer that provides the best response to each question. Please be sure to use a pencil and copletely fill the circle corresponding to your choice. If you change an answer, the previous ark ust be copletely erased. Your score on this ultiple choice test will be your nuber of correct answers. There is no penalty for guessing. It is to your advantage to answer every question. Calculators are not allowed to use. g = s -. A driver travels three-fourth distance of his journey at a velocity (v) and copletes rest of the journey at one half of his original velocity (½v). What was his average speed for the trip? [].85v [].8v [].75v [4].7v.65v. Sunil and Raesh push a kg block horizontally in the sae direction. Sunil pushes with a force of 5 N and Raesh pushes with a force of N. If a frictional force provides N of resistance, what is the acceleration of the block? []. s - []. s - [].87 s - [4].75 s -.5 s -. A unifor kg cylinder rests on a laboratory trolley as shown. The coefficient of static friction between the cylinder and the trolley is.5. If the cylinder is 4 c in diaeter and c in height, which of the following is closest to the iniu acceleration of the trolley needed to cause the cylinder to tip over? [] s - [] 4 s - [] 5 s - [4] 6 s - The cylinder would tip over at all of these accelerations.

2 4. A ball is thrown upward near the surface of the earth with a velocity of 5 s -. After 5 s later its velocity becoes zero oentarily. If the ball were thrown up with the sae velocity on Planet X, after 5 s it would still be oving upwards at s -. (Neglect air resistance) The ratio of is equal to The agnitude of the gravitational field intensity near the surface of planet X The agnitude of the gravitational field intensity near the surface of the earth [].6 [].8 [].5 [4] Two light plastic bags of negligible ass are placed eters apart. Each bag contains 5 angoes. If angoes were oved fro one bag to the other, the gravitational force between the two bags would [] increase to / the original value. [] decrease to /5 the original value. [] increase to 5/ the original value. [4] decrease to 5/9 the original value. not change. 6. A large balloon filled with air is dropped fro the ceiling of a school lab to the floor about below. Which of the following graphs would best represent the variation of its velocity (v) with tie (t) if the balloon coes down vertically? [] [] [] [4] 7. A driver in a 5 kg car wishes to pass a slow oving bus on a two lane road. What is the average power in watts required to accelerate the car fro s - to 4 s - in s? [], [], [], [4], 4,

3 8. A 4 kg ass is attached to a horizontal light spring with a spring constant of 5 N -. If the ass rests on a frictionless horizontal surface, what is the total energy of this syste when the ass set into siple haronic otion by an original displaceent of.? [] J [] J [] 5 J [4] 4 J, J 9. Two skaters on a frictionless icy surface push apart fro one another. One skater has a ass M uch greater than the ass of the second skater. After soe tie the two skaters are at a distance d apart. How far has the lighter skater oved fro her original position? [] d [] M d [] d [4] M d M + d M M +. Given three asses are connected as shown in the diagra. If the coefficient of kinetic friction between the large ass ( ) and the table is µ, what would be the upward acceleration of the sall ass ( )? The ass and friction of the cords and pulleys are sall enough to produce a negligible effect on the syste. [] g + + [] g( + + µ ) + [] gµ ( + + ) [4] gµ ( + + ) g( µ ) + +

4 4. An object with a ass of kg is accelerated fro rest. The graph above shows the variation of the agnitude of the net force with tie. At t = 4 s the object s speed would have been closest to which of the following: []. s - [].5 s - [] 5.8 s - [4] 7. s -.5 s -. A thin ring of ass and radius r rolls across the floor with a velocity v. Which of the following expression would be the best estiate of the ring s total kinetic energy as it rolls across the floor? [] v [] v [] v [4] v v + 4 r v v r. A 4. kg ass is attached to one end of a rope of long. If the ass is swung in a vertical circle fro the free end of the rope, what is the tension in the rope when the ass is at its highest point if it is oving with a speed of 5 s -? [] 5.4 N []. N [].6 N [4] 5 N 9. N 4. A ole of an ideal gas at STP is heated in an insulated container of constant volue until the average speed of its olecules doubled. Its pressure would therefore increase by a factor of [].5 [] [] [4] 4 8

5 5 5. If g of ice at C is ixed with g of boiling water at C, which of the following graphs would best represent the variation of teperature vs tie (t) of the two coponents of the ixture? [] [] [] [4] 6. A wave produced by a siple haronic oscillator whose displaceent in eters is given by the equation: y =. sin (πx + 4πt), what is the frequency? [] Hz [] 7. Hz [] 8 Hz [4] Hz 4 Hz 7. Which of the following wave properties cannot be deonstrated by all kinds of waves? [] Polarization [] Diffraction [] Superposition [4] Refraction Reflection 8. A source when at rest in a ediu produces waves to the right with a velocity v and a wavelength ofλ. If the source is set in otion to the left with a velocity v S ( v S < v ), what would be the agnitude of the wavelengths produced directly in front of the source? [] v S λ v [] v + S v λ v [] λ [4] vs λ v v v S λv v + v S

6 6 9. What would be the total current being supplied by the battery of negligible internal resistance in the circuit shown? Ω 4 Ω 6 Ω Ω 9V 4 Ω []. A [].5 A []. A [4].5 A. A. Consider a siple circuit containing a battery of negligible internal resistance and three identical light bulbs. Bulb A is wired in parallel with bulb B and this cobination is wired in series with bulb C. What would happen to the brightness of the other two bulbs if bulb A were to burn out? [] only bulb B would get brighter. [] both would get brighter. [] bulb B would get brighter and bulb C would get dier. [4] bulb B would get dier and bulb C would get brighter. There would be no change in the brightness of either bulb B or bulb C.. A circular coil of wire is oved vertically at a constant velocity through a horizontal agnetic field. The plane of the coil is perpendicular to the agnetic field. Which of the following graphs would best represent the electric current (I) induced in the coil with tie (t), if it started soewhat above the agnetic field and ended equally as far below the agnetic field? [] [] [] [4]

7 7. Which of the following graphs best represents the teperature (T) dependence of the resistivity ( ρ ) of an undoped seiconductor? [] [] [] [4]. An infinite slab of dielectric aterial with dielectric constant K and perittivity ε ( = Kε ) is placed in a unifor electric field of agnitude E. The field is perpendicular to the surface of the slab, as shown in the figure above. The electric field intensity inside the slab is. [] K E [] E Kε [] E [4] Kε E KE

8 8 4.. A wire is bent into an arc of radius R and subtended angleθ, as shown in the figure above. Point P is at the centre of the circular segent. The wire carries current I. The agnitude of the agnetic flux density at the point P is [] [] µ Iθ ( π ) R [] µ Iθ 4πR [4] µ Iθ 4πR µ I θr 5. The distribution of relative intensity [I(λ )] of blackbody radiation eitted fro a solid object versus the wavelength (λ ) is shown in the figure above. If the Wien displaceent constant is.9 - K, what is the approxiate teperature of the object? [] K [] 5 K [] 5 K [4] 5 K 65 K 6. A satellite of ass orbits a planet of ass M in a circular orbit of radius R. The tie required for one revolution is [] independent of M [] proportional to [] proportional to R [4] proportional to R / proportional to R

9 9 7. An infinite, uniforly charged sheet with surface charge density σ cuts through a spherical Gaussian surface of radius R at a distance x fro its centre, as shown in the figure above. The flux of the electric field intensityφ through the Gaussian surface is [] πr σ ε [] 4πR σ ε [] π ( R x) σ ε [4] π ( R x ε ) σ 8. Before Collision After Collision A particle of ass oving along the x-axis with speed v collides with a particle of ass initially at rest. After the collision, the first particle has coe to rest, and the second particle has split into two equal-ass pieces that ove at equal angleθ with the x-axis, as shown in the figure above. Which of the following stateents correctly describes the speeds of the two pieces? [] Both pieces ove with speed v. [] One of the pieces oves with speed v, the other oves with speed less than v. [] Both pieces ove with speed v/. [4] One of the pieces oves with speed v/, the other oves with speed greater than v/. Both pieces ove with speed greater than v/.

10 9. Which of the following best illustrates the acceleration of a siple pendulu bob at points a through e? [] [] [] [4]. A straight and light rod pivots about one end in a vertical plane. In configuration I, two sall identical asses are attached to the free end and in configuration II, one ass is oved to the centre of the rod as shown in the above figure. The ratio of The frequency of sall oscillations of configuration II The frequency of sall oscillations of configuration I is equal to [] [] 5 6 [] 6 5 [4]