chapter 7 and 8

Why does bending your legs when running enable you to swing your legs to and move more rapidly? Bending your legs shortens them, thus reducing rotational inertia. Bending your legs decreases the angular speed, thus reducing rotational inertia. Bending your legs puts the rotational axis in the center of the leg, thus reducing rotational inertia. Bending your legs increases the height of the foot, thus reducing rotational inertia.

Bending your legs shortens them, thus reducing rotational inertia.

How does the force needed to turn the wrench change if you increase the lever arm? It stays the same. It increases. It decreases.

It decreases.

As distance increases between most of the mass of an object and its center of rotation, how does rotational inertia change? It decreases. It goes to zero. It increases. It stays the same.

It increases.

What happens to the kinetic energy of a moving object if the net work done is positive? It decreases. It drops to zero. It remains the same. It increases.

It increases.

Is it easier to balance a long rod with a mass attached to it when the mass is closer to your hand or when the mass is farther away? It is equally easy in both cases. It is easier when the mass is closer to your hand. It is easier when the mass is farther from your hand.

It is easier when the mass is farther from your hand.

What is meant by the "lever arm" of a torque It is the distance between the point at which a force is applied and the center of mass of an object. It is the angle between the applied force vector and the rotational axis. It is the distance between the point at which a force is applied and the rotational axis. It is the perpendicular distance from the rotational axis to the line along which the force acts.

It is the perpendicular distance from the rotational axis to the line along which the force acts.

How does the rotational inertia of the rod with the mass toward the bottom compare with the rotational inertia of the mass toward the top? The rotational inertia of the rod with the mass closer to the bottom is greater than the rotational inertia of the rod with the mass closer to the top. The rotational inertia of the rod with the mass closer to the top is greater than the rotational inertia of the rod with the mass closer to the bottom. The rotational inertia of the rod with the mass closer to the top is equal to the rotational inertia of the rod with the mass closer to the bottom.

The rotational inertia of the rod with the mass closer to the top is greater than the rotational inertia of the rod with the mass closer to the bottom.

When you cut a broom right through the center of gravity, how do the weights of the two sides of the broom compare? The shorter side, where the bristles of the broom are, has a greater weight than the handle. Both sides of the broom on either side of the center of gravity have equal weight. The longer side (the handle) has a greater weight than the bristle side.

The shorter side, where the bristles of the broom are, has a greater weight than the handle.

An object of mass 1 kg that is moving in a straight line on a level surface slows down from 2 m/s to rest. What is the net work done on the object? -2 Joules -8 Joules 2 Joules 8 Joules

-2 Joules

A container with a mass of 5 kg is lifted to a height of 10 m. How much work is done by the gravitational force? 5000 Joules 0 Joules 50 Joules 500 Joules

500 Joules

A container with a mass of 5 kg is lifted to a height of 10 m. How much work is done by the gravitational force? 5000 Joules 0 Joules 500 Joules 50 Joules

500 Joules

How do clockwise and counterclockwise torques compare when a system is balanced? The clockwise torque is greater. They are both zero. They are equal in magnitude and opposite in direction. The counterclockwise torque is greater.

They are equal in magnitude and opposite in direction.

To double the rotational speed the centripetal force must _______. increase stay the same double be four times larger

be four times larger

When traveling three times as fast your kinetic energy is increased _______. by two times by four times by six times by nine times

by nine times

The torque exerted by a crowbar on an object increases with increased _______. force and leverage distance force rotational inertia energy of application

force and leverage distance

Rotational inertia of an object rotating about an axis becomes greater with _______. increased mass decreased mass decreased mass and decreased distance to mass concentration increased mass and increased distance to mass concentration

increased mass and increased distance to mass concentration

The rotational speed of every point of a rotating rigid object _______. is zero depends on the distance to the axis of rotation is the same is tangent to the circular motion

is the same

To improve the performance of a racing bicycle, the mass of the tires and rims is reduced so there is ____________. less friction less rotational inertia more rotational inertia less air resistance

less rotational inertia

A car drives up a steeply inclined ramp. The work done on the car by the Earth's gravitational force is ____. positive then negative positive negative zero

negative

An old man and his grandchild, both of the same mass, go up the stairs to their first-floor apartment. The old man gets to the apartment well before his grandchild. Which one delivered more power? the grandfather the child not enough information both delivered the same power

the grandfather

During a certain time interval, the net work done on an object is zero joules. We can be certain that ____. the object was at rest at the end of this interval the object was at rest during this entire interval the object's final speed was the same as its initial speed

the object's final speed was the same as its initial speed

During a certain time interval, the net work done on an object is zero joules. We can be certain that ____. the object was at rest during this entire interval the object was at rest at the end of this interval the object's final speed was the same as its initial speed

the object's final speed was the same as its initial speed

The work that is done when twice the load is lifted one-half the distance is _______. twice as much the same one half as much four times as much

the same

Two identical cars are driving in opposite directions at the same speed. Their kinetic energies have ____. different magnitudes, but the same sign different magnitudes and opposite signs the same magnitude, but opposite signs the same magnitude and sign

the same magnitude and sign

Two identical cars are driving in opposite directions at the same speed. Their kinetic energies have ____. the same magnitude, but opposite signs different magnitudes, but the same sign the same magnitude and sign different magnitudes and opposite signs

the same magnitude and sign

A solid sphere and a hollow sphere (spherical shell) of the same mass and same radius rotate with the same amount of kinetic energy. Which one is rotating faster? Neither; they must be rotating at the same speed. the hollow sphere the solid sphere

the solid sphere

When one does four the work in twice the time, the power expended is _______. the same one half as much twice as much three times as much

twice as much

When one does four the work in twice the time, the power expended is _______. three times as much the same twice as much one half as much

twice as much

When you lift the load twice as high, in half the time, the increase in potential energy is _______. the same four times as much half as much twice as much

twice as much

A spacecraft moves around Earth in a circular orbit with a constant radius. How much work is done by the gravitational force on the spacecraft during one revolution? m g h zero F d

zero

Why does the rotational inertia of the rod with the attached mass closer to your hand compare the way it does with the rotational inertial of the rod with the attached mass farther away? Rotational inertia depends on whether the mass is farther or closer to the point of rotation. The farther the mass is, the higher the rotational inertia. Rotational inertia depends on whether the mass is farther or closer to the point of rotation. The closer the mass is, the higher the rotational inertia. Rotational inertia depends on whether the mass is lower or higher. Objects where the mass is higher have a greater rotational inertia.

Rotational inertia depends on whether the mass is farther or closer to the point of rotation. The farther the mass is, the higher the rotational inertia