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Rotational Dynamics

Total questions: 12

Worksheet time: 12mins

Name
Class
Date
1.

A rigid body is rotating about an axis. to stop the rotation, we have to apply........

a)

pressure

b)

force

c)

momentum

d)

torque

2.

A disc of mass 2 kg and radius 20 cm is free rotate about an axis through its centre and perpendicular to the disc. If a force of 50 N is applied tangentially to the disc, then the angular acceleration is.......

a)

250 rad/s2

b)

25 rad/s2

c)

2.5 rad/s2

d)

0.25 rad/s2

3.

A circular disc rotates about an axis passing through its center with a certain angular velocity. Suddenly a small piece of the disc breaks from the edge and falls down. Then ........

a)

its rotational inertia will increase and the angular velocity will decrease

b)

its rotational inertia will decrease and the angular velocity will increase

c)

both, the rotational inertia and the angular velocity will increase

d)

both, the rotational inertia and the angular velocity will decrease

4.

The rotational inertia of a body does not depend on ......

a)

the mass of the body

b)

the angular velocity of the body

c)

the axis of rotation of the body

d)

the distribution of the mass of the body

5.

An object with a rotational inertia of 5 kg-m2 rotating with an angular velocity of 6 rad/s has the same kinetic energy as a mass of 20 kg moving with a velocity of ........

a)

12m/s

b)

9 m/s

c)

6 m/s

d)

3 m/s

6.

Which has greater angular velocity, a horse near the outside rail of a merry-go-round or a horse near the inside rail?

a)

The inside horse

b)

The outside horse

c)

Neither - they both have the same angular velocity

7.

The easiest way to open a heavy door is by applying the force

a)

Near the hinges

b)

In the middle of the door

c)

At the edge of the door far from the hinges

d)

At the top of the door

8.

An ice skater is spinning in a circle with his arms extended out. He then brings his arms in, what happens to his rotational velocity?

a)

It increases

b)

It decreases

c)

It stays the same

d)

He stops spinning immediately

9.

Because a hollow ball has a higher rotational inertia than a solid ball...

a)

The solid ball rolls faster

b)

The solid ball weighs more.

c)

The solid ball weighs less.

d)

They both accelerate at the same rate.

10.
A cylinder (I=1/2mr2) and a hoop (I=mr2) of the same radius and same mass are traveling at the same angular velocity (ω).  What is the ratio of the rotational kinetic energy of the cylinder to the rotational kinetic energy of the hoop?
a)
1:1
b)
1:2
c)
2:1
d)
1:4
11.

What is the total kinetic energy of a 3 kg solid disk ( I=12mR2I=\frac{1}{2}mR^2  ) with a diameter of 80 cm rolling at 4 m/s?

a)

12 J

b)

24 J

c)

36 J

d)

48 J

12.

The figure shows scale drawings of four objects, each of the same mass and uniform thickness, with the mass distributed uniformly. Which one has the greatest rotational inertia when rotated about an axis perpendicular to the plane of the drawing at point P?

a)

A

b)

B

c)

C

d)

D