Rotational Motion and Gravitation — Practice

Question 1

The moment of inertia of a ring of mass M and radius R about its central axis (perpendicular to its plane) is

Accepted Answer

A

Question 2

The moment of inertia of a solid sphere of mass M and radius R about a diameter is

Accepted Answer

A

Question 3

A force of 20 N acts at 15 cm from a bolt, at 30° to the spanner. The torque about the bolt is

Accepted Answer

A

Question 4

A thin rod of mass M and length L has moment of inertia ML²/12 about its centre. About an axis through one end (perpendicular to the rod), it is

Accepted Answer

A

Question 5

A disc has moment of inertia ½MR² about its central axis. Its moment of inertia about a diameter is

Accepted Answer

A

Question 6

A skater spinning with moment of inertia I at angular velocity ω pulls in her arms so her moment of inertia halves. Her new angular velocity is

Accepted Answer

A

Question 7

A disc of moment of inertia I rotating at angular velocity ω has an identical stationary disc dropped coaxially onto it, so they rotate together. The common angular velocity is

Accepted Answer

A

Question 8

A constant torque of 5 N·m acts for 4 s on a body of moment of inertia 2 kg·m², initially at rest. Its final angular velocity is

Accepted Answer

A

Question 9

A solid sphere, a disc and a ring (same mass and radius each) roll from rest down the same incline. Which reaches the bottom first?

Accepted Answer

A

Question 10

For a solid sphere rolling without slipping, the fraction of its total kinetic energy that is rotational is

Accepted Answer

A

Question 11

If the distance between two point masses is doubled, the gravitational force between them becomes

Accepted Answer

A

Question 12

At a height equal to the Earth's radius above the surface, the acceleration due to gravity is (surface value g)

Accepted Answer

A

Question 13

At a depth equal to half the Earth's radius below the surface, the acceleration due to gravity is (surface value g, uniform Earth)

Accepted Answer

A

Question 14

The escape velocity from the surface of the Earth is approximately

Accepted Answer

A

Question 15

Two satellites orbit the Earth at radii r and 4r. The ratio of their periods (T at 4r : T at r) is

Accepted Answer

A

Practice — Rotational Motion and Gravitation

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