6 System of Particles and Rotational Motion

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Prepared by Vinodkumar M, HSST Physics, St. Aloysius HSS, Elthuruth, Thrissur

1. In which spinning poss does the ballet dancer have lesser angular velocity? *

1 point

Fig b

Fig a

2. A solid sphere of mass m and radius r starts from rest and rolls down an inclined plane as in fig. (a) Moment of inertia of the sphere about an axis passing through center is ............ *

1 point

(m r^2)/2

2/5 m r^2

2/3 m r^2

(m r^2)/4

2 (b) Find the velocity when it reaches the ground *

3 points

Square root of (10gh/3)

Square root of (10 gh/7)

Square root of (gh/7)

Squrare root of (gh/3)

Other:

3. A solid cylinder of mass 20 kg rotates about its axis with an angular speed of 100 rad/s. The radius of the cylinder is 0.25 m. The magnitude of angular momentum of the cylinder about its axis is .......... *

2 points

6.25 Js

62.5 Js.

0.625 Js

625 Js

4. A thin circular ring is rotating about its axis. Which theorem helps us to find the moment of inertia of the ring about its diameter? *

1 point

Perpendicular axes theorem

Parallel axes theorem

5. A ring rolls down an inclined plane without slipping. The velocity of the ring on reaching the ground is ....... *

2 points

Square root of (10 gh/7)

Square root of (gh)

Square root of (gh/2)

Square root of (4gh/3)

6. The moment of inertia of two rotating bodies A and B are IA and IB (IA > IB) and their angular momentum are equal. Which one has greater KE? *

2 points

Body A

Body B

7. Moment of inertia of a ring about an axis passing through center is MR^2. The moment of inertia about diameter is ..................... *

1 point

(MR^2)/4

2/3(MR^2)

(MR^2)/2

8. A coin is rolling on a plane surface. What fraction of its total kinetic energy is rotational? *

3 points

1/2

1/3

1/4

9. Two identical concentric rings each of mass M and radius R are placed perpendicular to each other. What is the moment of inertia about an axis passing through the center of this system? *

1 point

3 MR^2

1/4 MR^2

2MR^2

3/2 MR^2

Option 5

10. The mathematical relation connecting angular momentum (L) and torque (T) is .............. *

1 point

T = dL/dt

L = dT x dt

L = dT/dt

T = dL x dt

11. A solid sphere is rotating about a diameter at an angular velocity ω. If it cools so that its radius is reduced to 1/n of its original value, its angular velocity becomes............. *

1 point

ω/n

ω/n^2

n^2 ω

nω

12. The rotational analogue of force is moment of force, also called ......... *

1 point

Angular momentum

Torque

Force

Momentum

13. The turning effect of force is maximum when the angle between vector r and vector F is ............. *

1 point

30 degree

180 degree

0 degree

90 degree

14. A wheel starting from rest acquires an angular velocity of10 rad/s in two seconds. The moment of inertia of the wheel is 0.4 kg m^2. The torque acting on it .................. *

2 points

4 N m

2 N m

1 N m

3 N m

15. The possibility of falling backward with the ladder is more when you are high up on the ladder than when you just begin to climb. Because............. *

1 point

torque decreases with distance from the origin

the ladder tends to slip

torque increases with distance from the origin

none of these

16. Classical dancers bring their hands close to their bodies to rotate faster. The principle employed by them is............. *

1 point

Law of conservation of linear momentum

Law of equipartition of energy

Law of conservation of angular momentum

Law of conservation of energy

17. The rotational analogue of mass is ................ *

1 point

Moment of inertia

Angular momentum

Torque

Inertia

18. The equation connecting angular momentum and linear momentum is *

1 point

iii

19. The moment of inertia of a circular disc about an axis perpendicular to the plane, through the center is ...... *

1 point

3/2 MR^2

MR^2 / 4

MR^2 / 2

MR^2 / 6

20. In translatory motion, angular momentum *

1 point

may be present

is always greater than one

is always zero

is always infinite

21.The equation connecting torque T with force F *

1 point

F = r + T

F = r x T

T = r x F

T = F / r

22. A meter stick is balanced at its center (50 cm). When two coins, each of mass 5 g, are put one on the top of the other at the 12 cm mark, it is found to be balanced at 45 cm. What is the mass of the stick? *

2 points

6.6 g

100 g

66 g

10 g

23. The moment of inertia of a thin rod of mass M and length I about an axis perpendicular to the rod at its midpoint is Ml^2/12. The moment of inertia of the rod about an axis perpendicular to it and passing through one end of the rod. *

2 points

Ml^2 / 3

Ml^2

Ml^2 / 6

Ml^2 / 4

24. The rotational analogue of linear displacement is *

1 point

angular acceleration

angular velocity

angular displacement

angular momentum

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