Pre-Lecture Quiz 12

If the net work done on an object is positive, what can you conclude about the object's motion? Assume the object is in the absence of any other forces or friction. The object is at rest; its position is constant. The object is slowing down. The object is moving with a constant velocity. The object is speeding up.

The object is speeding up

An object weighing 20 N moves horizontally toward the right a distance of 5.0 m. What is the work done on the object by the force of gravity? The work done on the object by the force of gravity is zero joules. The work done on the object by the force of gravity is 0.25 J. The work done on the object by the force of gravity is 4.0 J. The work done on the object by the force of gravity is 100 J. The work done on the object by the force of gravity is 50 J.

The work done on the object by the force of gravity is zero joules.

A ball is thrown straight upward. How does the sign of the work done by gravity while the ball is traveling upward compare with the sign of the work done by gravity while the ball is traveling downward? Work done by gravity is positive while the ball is traveling both upward and downward. Work done by gravity is negative while the ball is traveling upward and positive while the ball is traveling downward. Work done by gravity is positive while the ball is traveling upward and negative while the ball is traveling downward. Work done by gravity is negative while the ball is traveling both upward and downward.

Work done by gravity is negative while the ball is traveling upward and positive while the ball is traveling downward.

The amount of kinetic energy an object has depends on its mass and its speed. Rank the following sets of oranges and cantaloupes from least kinetic energy to greatest kinetic energy. If two sets have the same amount of kinetic energy, place one on top of the other. (1) mass: m and speed: v; (2) total mass: 2 m and speed: 1/2 v; (3) mass: 4 m and speed: 1/4 v; (4) total mass: 4 m and speed: v; (5) mass: 4 m and speed: v

least KN: 3, 2, 1, 4 and 5 most KN

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

negative When an object's displacement has a component in a direction opposite that of a given force, that force does negative work on the object.

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's final speed was the same as its initial speed the object was at rest during this entire interval.

the object's final speed was the same as its initial speed When the net work done on an object is zero, there is no overall change in the object's kinetic energy.

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

the same magnitude and sign. The kinetic energy of a moving object is always positive, regardless of the direction it is moving in, or the coordinate system used.