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ANNUAL EXAMINATION - PHYSICS
CLASS XI
Time: 3 Hours
Max Marks: 70
General Instructions
(a) All questions are compulsory.
(b) Questions 1-8 carry one mark each
(c) Questions 9-18 carry two marks each
(d) Questions 19-27 carry three marks each
(e) Questions 28-30 carry five marks each
(f) Use of calculator is not allowed.
……………………………………………………………………………………………………………………………………………………
1.
If x = a + bt +ct2, where ‘x’ is in metre and t in second. What is the unit of ‘c’?
(1)
2. A cubical block rests on an inclined plane of µ= 1/√3. Determine the angle of friction.
(1)
3. What is the work done by a force F = 3i + j if the displacement of the body is s = 2k?
(1)
4. If the torque acting on a particle about the origin is zero, what can we say about the angular
momentum of the particle about the origin?
(1)
5. Why are rain drops spherical?
(1)
6. Why do we prefer steel to copper in the manufacture of spring?
(1)
7. At what temperature does all molecular motion cease? Explain.
(1)
8. Two sound sources produce 12 beats in 4 seconds. By how much do their frequencies differ?(1)
9. Check the correctness of the relation ρ = 3g/4 πrG where ρ is density, g is acceleration due to
gravity, r is radius and G is gravitational constant.
(2)
10. A man can jump on moon six times as high as on the earth. Explain why?
(2)
11. A light and a heavy body have same kinetic energy. Which one has larger momentum and why?
(2)
12. State the theorems of parallel and perpendicular axes on moment of inertia.
(2)
13. What are the essential conditions for a satellite to appear stationary?
(2)
14. Even the carnot heat engine cannot give 100% efficiency, Explain why?
OR
A carnot engine has the same efficiency when operated between 500 K and 100 K or between
900 K or T K. Find the value of temperature T.
(2)
15. State any four postulates of kinetic theory.
(2)
16. Find the temperature at which root mean square velocity of a gas is half of its value at 0oC,
pressure remaining constant.
(2)
17. Find the distance from mean position at which the kinetic energy of a simple harmonic oscillator
is equal to its potential energy?
(2)
18. The displacement y of a particle in a medium is y = 10-6 sin (100 t + 20x + π/4), where t is in
second, and x in metre. What is the speed of the wave?
(2)
19. Derive expression for centripetal acceleration of an object in a uniform circular motion in a
plane.
(3)
20. (a). Why is it easier to pull than to push a lawn roller?
(b). Why are wheels made circular?
(3)
21. (a). Why does a gun recoil when it is fired?
(b). A gun weighing 10 kg fires a bullet of 50 gram with the velocity of 500 m/s. With what
velocity does the gun recoil?
(3)
22. (a). What is the need for banking of roads?.
(3)
(b). Derive the expression for the maximum speed of a vehicle on the banked road. Neglect the
force of friction between the tyres and the road.
23. (a)Define elastic and inelastic collision.
(3)
(b) A lighter body collides with a much more massive body at rest. Prove that the direction of
lighter body is reversed and massive body remains at rest.
24. On a two lane road, car A is travelling with a speed of 36 km/h. Two cars B and C approach car
A in opposite directions with a speed of 54 km/h each. At a certain instant, when the distance
AB is equal to AC, both being 1km, B decides to overtake A before C does. What minimum
acceleration of car B is required to avoid an accident?
(3)
B •
A
•
•C
25. Define acceleration due to gravity. Show that gravity decreases with depth.
(3)
26. Derive an expression for the excess of pressure inside a soap bubble.
(3)
27. Derive Mayer’s formula Cp – Cv = R
OR
Derive expression for work done during an isothermal expansion.
(3)
28. What is the phenomenon of capillarity? Derive an expression for the rise of liquid in a capillary
tube of uniform diameter. Explain, why the liquid rises more in a narrow tube and less in a
wider tube?
OR
Define terminal velocity. Derive an expression for the terminal velocity of a sphere falling
through a viscous fluid.
(5)
29. (a). Derive the relations for the kinetic energy, potential energy and total energy of a body
executing S.H.M. In what positions, the energy is wholly kinetic or wholly potential?
(b). Plot a graph of kinetic energy, potential energy and total energy of the oscillator with
displacement from mean position.
OR
State Newton’s formula for velocity of sound in gases. Discuss Laplace correction. What is the
effect of density, pressure and temperature on the velocity of sound in air? Explain.
(5)
30. (a)Derive expression for horizontal range of a projectile fired with a speed u at an angle θ with
the horizontal. Prove that the horizontal range of the projectile is same, when fired at an angle
θ and (90-θ) with the horizontal.
(b) A flywheel is making 60 rpm. Calculate the linear speed of the point on its rim. The radius of
the wheel is 3m.
OR
(a). Define relative velocity of an object with respect to another. Draw position – time graphs of
two objects moving along a straight line, when their relative velocity is (i) zero and (ii) non-zero.
(b). How long will a passenger sitting at the window of a train travelling at a speed of 54 Km/h
see a train passing by in the opposite direction with a speed 36 Km/h, if the length of the second
train is 150 m?
(5)