10.5 Angular Momentum and Its Conservation

In case of human motion, one would not expect angular momentum to be conserved when a body interacts with the environment as its foot pushes off the ground. Astronauts floating in space aboard the International Space Station have no angular momentum relative to the inside of the ship if they are motionless. Their bodies will continue to have this zero value no matter how they twist about as long a…

Which rotational system would be best to use as a model to measure how angular momentum changes when forces on the system are changed?

1. a fishing reel
2. a planet and its moon
3. a figure skater spinning
4. a person's lower leg

Which torque applied to a disk with radius 7.0 cm for 3.5 s will produce an angular momentum of 25 N•m•s?

1. 7.1 N•m
2. 357.1 N•m
3. 3.6 N•m
4. 612.5 N•m

A hamster sits 0.10 m from the center of a lazy Susan of negligible mass. The wheel spins with a frequency of 1.0 rev/s. How will the frequency of the lazy Susan change if the hamster walks to 0.30 m from the center of rotation? Assume zero friction and no external torque.

1. It will speed up to 2.0 rev/s.
2. It will speed up to 9.0 rev/s.
3. It will slow to 0.11 rev/s.
4. It will slow to 0.22 rev/s.

Consider system A, consisting of two disks of radius R, with both rotating clockwise. Now consider system B, consisting of one disk of radius R rotating counterclockwise and another disk of radius 2R rotating clockwise. All of the disks have the same mass, and all have the same magnitude of angular velocity.

Which system has the greatest angular momentum?

1. A
2. B
3. They're equal.
4. Not enough information

(a) Calculate the angular momentum of the Earth in its orbit around the Sun.

(b) Compare this angular momentum with the angular momentum of Earth on its axis.

Suppose you start an antique car by exerting a force of 300 N on its crank for 0.250 s. What angular momentum is given to the engine if the handle of the crank is 0.300 m from the pivot and the force is exerted to create maximum torque the entire time?

Three children are riding on the edge of a merry-go-round that is 100 kg, has a 1.60-m radius, and is spinning at 20.0 rpm. The children have masses of 22.0, 28.0, and 33.0 kg. If the child who has a mass of 28.0 kg moves to the center of the merry-go-round, what is the new angular velocity in rpm?