ANGULAR MOMENTUM

1. Suppose a child walks from the outer edge of a rotating merry-go round in towards the center of rotation. Does the angular velocity of the merry-go-round increase, decrease, or remain the same?

• Increases

• Decreases

• Remains the same

• More information is needed

1. What quantity determines whether or not angular momentum is conserved in a collision?

• A change in gravitational potential energy.

• A net external torque

• A change in angular speed

• A change in moment of inertia.

• None of the above

Why doesn’t a rapidly spinning toy gyroscope fall over?

• The conservation of angular momentum prevents it from falling, by requiring that there be no change in the angular momentum.

• The conservation of energy prevents it from falling, because it would gain kinetic energy if it did.

• There is no external torque which can cause it to fall.

• The net external torque is horizontal and in a direction perpendicular to the angular momentum.

A box with a mass of 2.0kg rests on one end of a seesaw. The seesaw is 6.0m long, and we can assume it has negligible mass. Approximately what magnitude of angular momentum (in kgm² /s) will the box have if someone with a mass of 65kg sits on the other end of the seesaw quickly, with a velocity of 1.2m/s?

• 200

• 234

• 235

• 243

• 253

Competitive divers pull their limbs in and curl up their bodies when they do somersaults. Just before entering the water, they fully extend their limbs to enter straight down. How does their angular velocity change when they fully extend their limbs?

• Increases

• Decreases

• Remains the same

• More information is needed

What will happen to a spinning ice skater if he extends his arms outward?

• You need data about the skater to answer this question.

• No outside torque means the skater will maintain the same speed.

• His rotational speed increases.

• His rotational speed decreases.

What factors could the skater change to apply the same amount of torque but increase the rate of his spin? Check all that apply.

• Gain weight

• Lose weight

• Pull his arms in

• Extend his arms

• Crouch down

Under what conditions is angular momentum conserved?

• always

• when the system is isolated

• when there is friction

• never