First, let us consider a sled of mass being pulled by a constant, horizontal force of magnitude along a rough, horizontal surface. The sled is speeding up. Part A. How many forces are acting on the sled?
1. one
2. two
3. three
4. four
5. Correct
Part B. The work done on the sled by the force of gravity is .
1. zero
2. negative
3. positive
Part C. The work done on the sled by the normal force is .
1. zero
2. negative
3. positive
Part D. The work done on the sled by the pulling force is .
1. zero
2. negative
3. positive
Part E. The work done on the sled by the force of friction is .
1. zero
2. negative
3. positive