Conceptual Physics Ch 07 & 08

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? 8 Joules -2 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? 500 Joules 0 Joules 5000 Joules 50 Joules

500 Joules

Why doesn't the Leaning Tower of Pisa topple over? The center of gravity is at the center of the building. A vertical line through the center of gravity passes inside its support base. The center of gravity is suspended below its support base. A vertical line through the center of gravity passes through the center of its support base.

A vertical line through the center of gravity passes inside its support base.

Why it is easier to remove an old bolt if we add an extension to the wrench handle? Because there is more mass. Because a higher force is applied. Because a higher torque is applied. Because the wrench is heavier.

Because a higher torque is applied.

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

It decreases.

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

It increases.

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

It increases.

Is it easier for a circus performer to balance a long rod held vertically with people hanging off the other end, or the same long rod without the people at the other end, and why? It is easier for the performer to balance a long rod held vertically without people at the other end because the rotational inertia is greater. It is easier for the performer to balance a long rod held vertically with people at the other end because the rotational inertia is greater. It is easier for the performer to balance a long rod held vertically with people at the other end because the rotational inertia is smaller. It is easier for the performer to balance a long rod held vertically without people at the other end because the rotational inertia is smaller.

It is easier for the performer to balance a long rod held vertically with people at the other end because the rotational inertia is greater.

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 easier when the mass is farther from your hand. It is easier when the mass is closer to your hand. It is equally easy in both cases.

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

Why is centrifugal force in a rotating frame called a "fictitious force"? Newton made it up. It is not a fundamental force of nature. Instead, it is a force that only appears in an accelerating frame of reference. It is a force physicists had to insert to make the equations work out right. An outside observer has to add in the centrifugal force to understand motion in a rotating frame of reference.

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

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 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 angle between the applied force vector and the rotational axis.

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 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.

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 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. Both sides of the broom on either side of the center of gravity have equal weight.

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

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

They are equal in magnitude and opposite in direction.

An object is thrown straight up. Which of the following is true about the sign of work done by the gravitational force while the object moves up and then down? Work is zero the way up, work is zero on the way down Work is positive on the way up, work is positive on the way down Work is negative on the way up, work is positive on the way down Work is negative on the way up, work is negative on the way down

Work is negative on the way up, work is positive on the way down

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

be four times larger

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

by nine times

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

force and leverage distance

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

four times as much

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

increased mass and increased distance to mass concentration

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

is the same

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

less rotational inertia

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

m g h

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

negative

A ruler is in equilibrium on the tip of your finger only if __________. the net torque is zero nobody touches the ruler net torque and net force are zero the net force is zero

net torque and net force are zero

When a rock tied to a string is whirled in a horizontal circle, doubling the speed _______. doubles the velocity, but the string tension remains the same decreases the velocity quadruples the tension in the string doubles the tension in the string

quadruples the tension in the string

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 both delivered the same power not enough information the child

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

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

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 _______. one half as much three times as much twice as much the same

twice as much

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

twice as much