PHYS 205 - HW8 - Rotational Motion, Torques, etc.

What is needed to change a system's angular momentum?

Angular momentum changes with an applied external torque.

At what part of a meterstick should you place your finger so that it will balance in a horizontal position?

At the 50-cm mark

To improve the performance of a racing bicycle the mass of the tires and rims are reduced, why?

Because there is less rotational inertia

As distance increases between most of the mass of an object and its center of rotation, how does rotational inertia change?

It increases

70-kg person sits 2.0 m from the center of a horizontally rotating platform with a tangential speed of 2.0 m/s. What is the angular momentum of the person?

L = 280 kg* m/s L = MVR = (70-kg) * (2.0 m) * (2.0 m/s) = 280 kg* m/s

Which varies with radial distance on a rotating turntable, tangential speed or rotational speed?

Tangential speed increases with distance. Rotational speed is constant.

Which of the following statements correctly describes the system shown in the figure?

The angular acceleration of the pulley is nonzero.

What happens when block B moves downward?

The cord's tension on the right side of the pulley is higher than on the left side.

Is it an inward force or an outward force that is exerted on the clothes during the spin cycle of a washing machine?

The tub of the machine exerts centripetal inward force on clothes.

How do clockwise and counterclockwise torques compare when a system is balanced?

They are equal in magnitude and opposite in direction.

When you whirl a can overhead by a string in a circular path, what is the direction of the force exerted on the can?

Toward the center of the circle.

The tangential speed on the outer edge of a rotating carousel is ___.

greater than toward the center

The rotational speed of every point of a rotating rigid object ___.

is the same

What are the units of measurement for tangential speed and rotational speed?

m/s for tangential, rpm for rotational