Pearson chapter 8

On a balanced seesaw, a boy three times as heavy as his partner sits

1/3 the distance from the fulcrum

A person having a mass of 80 kg sits on the edge of a horizontal rotating platform, 2.4 m from the center of the platform, and has a tangential speed of 1.6 m/s. Calculate the angular momentum of the person.

310 kg⋅m2s

Why can't you stand with your heels and back to a wall and then bend over to touch your toes and return to your stand-up position?

A vertical line through the center of gravity of your body is in front of the tips of your toes, which is outside your support base

Distinguish between linear momentum and angular momentum

Angular momentum depends on the distribution of mass, whereas linear momentum depends on the total mass

If a skater who is spinning pulls her arms in so as to reduce her rotational inertia by half, by how much will her angular momentum change? By how much will her rate of spin change?

Her angular momentum does not change. Her spin rate doubles.

Why is centrifugal force in a rotating frame called a "fictitious force"

It is not a fundamental force of nature. Instead, it is a force that only appears in an accelerating frame of reference.

Which will have the greater acceleration rolling down an incline: a hoop or a solid disk? Why?

The solid disk will because the mass is closer to the axis of rotation.

How does the tapered rim of a wheel on a railroad train allow one part of the rim to have a greater tangential speed than another part when it is rolling on a track

The tangential speed is proportional to the radius. The inside of the wheel rolls on a larger radius than the outside of the wheel.

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 at the end of a string in a circular path, what is the direction of the force you exert on the can?

Toward the center of the circle

A flywheel's diameter is twice that of another of the same shape and mass. Rotational inertia of the larger flywheel is

four times greater

Consider a string with several rocks tied along its length at equally spaced intervals. You whirl the string overhead so that the rocks follow circular paths. Compared with a rock at the end of the string, a rock at the middle moves

half as fast

If Earth rotated more slowly about its axis, your weight would

increase

If the world's populations moved to the North Pole and the South Pole, would the 24-hour day become longer, shorter, or stay the same?

shorter

The force responsible for a car moving steadily along a no-friction icy banked curve is due to

the radial component of the normal force.

Which tin can will roll down an incline in the shortest time, one filled with water or one filled with ice? (Hint: water 'slides' inside the can.)

with water