(Multiple choice)

(1)

A woman runs up a flight of stairs. The gain in her gravitational potential energy is U. If she runs up the same stairs with twice the speed, what will be her gain in potential energy

(a) U 

(b) 2U 

(c) U/2 

(d) 4U 

(e) U/4

(2)

Which of the following statements is true. 

(a) The kinetic and potential energies of an object must always be positive quantities. 

(b) The kinetic and potential energies of an object must always be negative quantities. 

(c) Kinetic energy can be negative, but potential energy cannot. 

(d) Potential energy can be negative, but kinetic energy cannot. 

(e) None of the preceding statements is true.

(3)

A block slides a certain distance down an incline. The work done by gravity is W. What is the work done by gravity if this block slides the same distance up the incline? 

(a) W 

(b) Zero 

(c) -W 

(d) Gravity can’t do work; some other force does work. 

(e) Cannot be determined unless given the distance traveled.

(4)

True or false: 

(a) Only conservative forces can do work. 

(b) If only conservative forces act, the kinetic energy of a particle does not change. 

(c) The work done by a conservative force equals the decrease in the potential energy associated with that force.

(5) True or false:

(a) The gravitational force cannot do work because it acts at a distance. 

(b) Work is the area under the force-versus-time curve.

(6)

Negative work by an applied force implies that 

(a) The kinetic energy of the object increases. 

(b) The applied force is variable. 

(c) The applied force is perpendicular to the displacement. 

(d) The applied force has a component that is opposite to the displacement. 

(e) Nothing; there is no such thing as negative work.

(7)

A movie crew is in the Badlands when their car over heats. After they stop to let it cool down, an argument breaks out. They agree that they must go easy on the engine, but they disagree about when the engine works the hardest, and therefore about how they should drive for the rest of the trip. Carolyn claims that the work done by the car in accelerating from 0 to 20 km/h is less than that required to accelerate from 20 to 30 m/h, meaning they should drive more slowly. Ted says no, the work done between 0 and 20 km/h is more than the work done between 20 and 30 km/h. Ernie says it all depends on the mass of the car, and Bloop say s it all depends on how long you take to change from one speed to another. Who is right?