Physics 121 General Physics
Concept Quizzes
Chapter 10 Rotation of a Rigid Object about a Fixed Axis
Chapter 11 Angular Momentum
Chapter 12 Static Equilibrium and Elasticity

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You are using a wrench and trying to loosen a rusty nut. Which of these arrangements will be the most effective in loosening the nut? (The diagrams are looking from below the nut.)

A 1.0 kg rock is suspended by a massless string from one end of a 1.0 m long measuring stick. What is the mass of the measuring stick if it is balanced by a support at the 0.25 m mark?

0.5 kg
1.0 kg
2.0 kg
4.0 kg

A boy and a girl are riding on a merry-go-round that is turning. The boy is twice as far as the girl from the merry-go-round's centre. If the boy and the girl are of equal mass, which statement is true about the boy's moment of inertia with respect to the axis of rotation?
It is four times the girl's.
It is twice the girl's.
It is the same for both.
The boy has greater moment of inertia but it is impossible to say how much more than the girl's it is.

Two wheels with fixed axels, each having a mass of 1.0 kg, start from rest and forces are applied as shown. Ignore the mass of the spokes and the hub so that I = mR2 for each. For both wheels to have the same angular acceleration, F2 must be

0.5 N
1.0 N
2.0 N
4.0 N

Two wheels initially at rest roll the same distance down an inclined plane without slipping. Wheel B has twice the radius but the same mass as wheel A. All the mass is concentrated at their rims so that their moments of inertias are I = mR2.

1. Which has more translational Kinetic Energy when it reaches the bottom of the incline?

Wheel A
Wheel B
Their Translational Kinetic Energies are the same.
We need more information to tell.

2. Which has the higher speed when it reaches the bottom of the incline?

Wheel A
Wheel B
Their speeds are the same.
We need more information to tell.

A car is traveling North. The traffic light ahead turns red, so the driver applies the brakes, slowing the car. As the car is slowing, in which direction is the angular acceleration of one of the wheels?

South.
East.
West.
Up.

Some children are riding on the outside edge of a merry-go-round. Ignore friction in the rotation of the merry-go-round. Consider the "system" of the children plus the merry-go-round. At the same time, the children all move towards the centre of the merry-go-round. When they do this

the angular momentum of the system stays constant.
the moment of inertia of the system stays constant.
the angular velocity of the system stays constant.
the merry-go-round slows down.

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