Half Yearly Paper

PHYSICS CLASS-XI M.Makrs-60

Questions 1 to 20 (1 Marks)

1. Which of the following quantities has a unit but dimensionless.

(a) Strain (b) Reynold’s number

(c) angular displacement (d) Poisson’s ratio

2. Random error can be eliminated by:

(a) careful observation

(b) eliminating the cause

(c) measuring the quantity with more than one instrument

(d) taking large number of observations and then their mean

3. Which of the following is the most accurate

(a) 200.0m (b) 20  101 m

(c) 2  10 2 m (d) data is inadequate

4. If f  x 2 , then the relative error in f is

2x  x 2 x
(a) (b) (c) (d)  x  2
x x x

5. The displacement of a particle starting from rest (at t = 0) is given by s  6t 2  t 3 . The time in
seconds at which the particle will attain zero velocity again, is:

(a) 2 (b) 4 (c) 6 (d) 8

6. A vehicle travels half the distance L with speed V1 and the other half with speed V2 , then its
average speed is:

V1  V2 2V1  V2 2V1 V2 2 V1  V2 

7. The given figure represents the displacement (x) time (t) graph for a particle in one dimensional
motion.
 Which of the figure given below represents the variation in velocity of the particle with time

(a) (b)

(c) (d)

8. The slope of the velocity time graph for retarded motion is

(a) positive (b) negative

(c) zero (d) can be + ve, –ve or zero

9. The angular speed of a fly-wheel making 120 revolutions/minute is

(a)  rad/sec (b) 4 rad/sec

(c) 2 rad/sec (d) 4 2 rad/sec

10. Figure along side shows a body of mass m moving with a uniform speed v along a circle of
radius r.

The change in velocity in going from A to B is

(a) v 2 (b) v/ 2 (c) v (d) Zero

11. A particle A is dropped from a height and another particle B is projected in horizontal direction
with speed of 5 m/sec from the same height, then correct statement is

(a) particle A will reach at ground first with respect to particle B

(b) particle B will reach at ground first with respect to particle A

(c) both particles will reach at ground simultaneously

12. The greatest height to which a man can through a ball is h. What is the greatest distance to
which he can throw the ball?

h h
(a) 2h (b) (c) (d) None
4 2

13. A rectangular block is placed on a rough horizontal surface in two different ways as shown,
then

(a) friction will be more in case (a)

(b) friction will be more in case (b)

(c) friction will be equal in both the cases

(d) depends on the relations among its dimensions

14. On increasing the smoothness of surfaces in contact,

(a) frictional force between them must decrease

(b) frictional force between them must increase

(c) frictional force between them first decreases then increases

(d) frictional force does not change as it does not depend on area of contact

15. When a horse pulls a cart, the horse moves down to

(a) the force exerted by horse on the cart

(b) the force exerted by the cart on the horse

(c) the force exerted by the horse on the earth

(d) the force exerted by the earth on the horse

16. A monkey is climbing up a rope, then the tension in the rope.

(a) must be equal to the force applied by the monkey on the rope

(b) must be less than the force applied by the monkey on the rope

(c) must be greater than the force applied by the monkey on the rope

(d) may be equal to, less than or greater the force applied by the monkey on the rope

17. Work done by all non-conservative forces is equal to:

(b) change in P.E. of the body

(c) change in total mechanical energy of the body

(d) none of these

18. Work done by a conservative force is positive if

(a) P.E. of the body increases

(b) P.E. of the body decreases

(c) K.E. of the body increases

(d) K.E. of the body decreases

19. A vehicle is moving with a uniform velocity on a smooth horizontal road, then power delivered
by its engine must be:

(a) uniform (b) increasing (c) decreasing (d) zero

20. A ball A of mass mA collide with a stationary ball B of mass mB . The ball A can come to rest
after collision if.

(a) mA  mB (b) mA  mB

(c) mA  mB (d) either (a) or (b)

Questions 21 to 26 (2 Marks)

21. State the principle of homogeneity of dimensions. Test the dimensional homogeneity of the
following equation:

1
h  h0  v0t  gt 2
2

22. A motor car moving with a uniform velocity of 20ms 1 comes to a stop, on the application of
brakes after travelling a distance of 10m. What is its acceleration?

23. Two springs A and B with spring constant k A and k B  k A > kB  are given. In which of the
spring more work is to be done, if

(a) they are stretched by the same amount

(b) they are stretched by same force

24. A skilled gunman always keeps his gun slightly tilted above the line of sight while shooting.
Why?

25. Derive a relation between linear and angular acceleration.

Questions 27 to 30 (4 Marks)

27. Assuming that the mass (m) of the largest stone that can be moved by a flowing river depends
on velocity (v), the density (s) and acceleration due to gravity (g). Derive an expression for it
dimensionally.

28. A ball is dropped and its displacement vs time graph is as shown figure. (displacement x is from
ground and all quantities are +ve upwards).

(a) Plot qualitatively velocity vs time graph.

(b) Plot qualitatively acceleration vs time graph

29. State and prove for the work energy theorem

30. A thin circular loop of radius R rotates about its vertical diameter with a an angular frequency
, Show that a small bead on the wire loop remains at its lowermost point for   g / R .
What is the angle made by the radius vector joining the center to the bead with the vertical
downward direction for   2 g / R ? Neglect friction.

Questions 31 & 32 (6 Marks)

31. Find the time of flight, maximum height, horizontal range of projectile projected from ground
with speed u and making an angle  with the horizontal direction.

32. State Newton’s third law of motion. Discuss its consequences.

VIAVA Questions

1. In free fall condition the initial velocity of a body may be zero or may not be zero. But
acceleration of the body is equal to__________.

2. The dimensional formula for relative density is_________

3. The ratio of the numerical values of the average velocity and average speed of a body is
always_________

4. In angular projection of a body the equation of trajectory in terms of horizontal range is y =

5. If a body is projected vertically upward in non-viscous medium, then time of asending is

7. A block of mass m is placed on a smooth inclined plane of inclination  with the horizontal.
The force exerted by the plane on the block has a magnitude ________

8. The magnitude of work done by a force depends on __________

9. Potential energy gradient is the component of ___________

10. The unit of coefficient of kinetic friction is __________