#### Model Paper 2

11th Standard

Reg.No. :
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Physics

Time : 01:00:00 Hrs
Total Marks : 45

Part-A

10 x 1 = 10
1. The center of mass of a system of particles does not depend upon,

(a)

position of particles

(b)

relative distance between particles

(c)

masses of particles

(d)

force acting on particle

2. A couple produces,

(a)

pure rotation

(b)

pure translation

(c)

rotation and translation

(d)

no motion

3. The speed of the center of a wheel rolling on a horizontal surface is vo  A point on the rim in level with the center will be moving at a speed of

(a)

zero

(b)

vo

(c)

$\sqrt{2}$vo

(d)

2vo

4. Two discs of same moment of inertia rotating about their regular axis passing through center and perpendicular to the plane of the disc with angular velocities ω1 and ω1. They are brought in to contact face to face coinciding with the axis of rotation. The expression for loss of energy during this process is,

(a)

$\frac{1}{4}$($(\omega _{1}-\omega _{2})^2$

(b)

$I((\omega _{ 1 }-\omega _{ 2 })^{ 2 })$

(c)

$\frac{1}{8}$I($(\omega _{1}-\omega _{2})^2$

(d)

$\frac{1}{2}I$($(\omega _{1}-\omega _{2})^2$

5. Four identical spheres each of mass m are placed at the corners of square of side 2 m. Taking the point of intersection of the diagonals as the origin the coordinates of the centre of mass are?

(a)

(1, 1)

(b)

(0,0)

(c)

(1, -1)

(d)

(-1, 1)

6. Two blocks of masses 20 kg and 5 kg are connected by a spring of negligible mass and placed on a frictionless horizontal surface. An impulse gives a velocity of 15 mls to the heavier block in the direction of lighter block. The velocity of centre of mass is

(a)

22 ms-1

(b)

30 ms-1

(c)

12 ms-1

(d)

15 ms-1

7. Which of the following has largest M.I

(a)

Ring about its axis perpendicular to its plane

(b)

Disc about its axis perpendicular to its plane

(c)

Solid sphere

(d)

Bar magnet

8. A dancer on ice spins faster when she folds her arms. This is due to

(a)

increase in energy & increase in angular momentum

(b)

increase in K.E & decrease in angular momentum

(c)

increase in K.E & constant in angular momentum

(d)

Decrease in friction at the skates

9. If the acceleration due to gravity becomes 4 times its original value, then escape speed

(a)

remains same

(b)

2 times of original value

(c)

becomes halved

(d)

4 times of original value

10. The kinetic energy of the satellite orbiting around the Earth is

(a)

equal to potential energy

(b)

less than potential energy

(c)

greater than kinetic energy

(d)

zero

11. Part-B

10 x 2 = 20
12. Two identical particles move towards each other with velocity 2 v and v respectively. The velocity of centre of mass?

13. A solid sphere of mass 20 kg and radius 0.25 m rotates about an axis passing through the center. What is the angular momentum if the angular velocity is 5 rad s-1.

14. If a comet suddenly hits the Moon and imparts energy which is more than the total energy of the Moon, what will happen?

15. If the Earth’s pull on the Moon suddenly disappears, what will happen to the Moon?

16. If the Earth has no tilt, what happens to the seasons of the Earth?

17. An unknown planet orbits the Sun with distance twice the semi-major axis distance of the Earth’s orbit. If the Earth’s time period is T1, what is the time period of this unknown planet?

18. Assume that you are in another solar system and provided with the set of data given below consisting of the planets’ semi-major axes and time periods. Can you infer the relation connecting semi-major axis and time period?

Planet
(imaginary)
Time period(T)
(in year)
Semi major axis (a)
(in AU)
Kurinji 2 8
Mullai 3 18
Marutham 4 32
Neithal 5 50
Paalai 6 72
19. Four particles, each of mass M and equidistant from each other, move along a circle of radius R under the action of their mutual gravitational attraction. Calculate the speed of each particle

20. Suppose unknowingly you wrote the universal gravitational constant value as G = 6.67 x 1011 instead of the correct value G = 6.67 x 1011, what is the acceleration due to gravity g' for this incorrect G? According to this new acceleration due to gravity, what will be your weight W'?

21. Calculate the gravitational field at point O due to three masses m1, m2 and m3 whose positions are given by the following figure. If the masses m1 and m2 are equal what is the change in gravitational field at the point O?

22. Part-C

5 x 3 = 15
23. What are the conditions in which force can not produce torque?

24. Give any two examples of torque in day-today life.

25. What is the relation between torque and angular momentum?

26. What is equilibrium?

27. How do you distinguish between stable and unstable equilibrium?