A box is being pulled up a rough incline by a rope connected to a pulley. Which of the following forces are doing work on box:
Choices: 1) Tension 2) Gravity 3) Kinetic Friction 4) Normal
Multiple Choice Answers:
a) 1, 2, 3, and 4
b) 1, 2, and 3
c) 1, 2, and 4
d) 1, 3, and 4
A diagram accompanies this problem but could not be included here.
I don't see the diagram so I can only guess. Work is done if there is a component of the force in the direction of motion. This would not be the case for the normal force, because by definition, it is going to be perpendicular to the surface and also to the motion. I would guess the others are doing work. Kinetic friction is probably doing negative work.