# Homework Help: Work on an object moving downards

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1. Oct 19, 2015

### AAAA

1. The problem statement, all variables and given/known data
You move a textbook from a high shelf to a low shelf. Is the work you do on it positive or negative?

2. Relevant equations
W = Fcosd

3. The attempt at a solution
My understanding is that if you are doing a positive applied force on the textbook, over some distance, the work should be positive. But the answer is negative. Why?

2. Oct 19, 2015

### brainpushups

In what direction is the force YOU exert? Compare this with the direction of motion.

3. Oct 19, 2015

### AAAA

The motion is upwards, the direction is downwards.

4. Oct 19, 2015

### brainpushups

That's not how you phrased the question:

From a high to a low shelf means the motion is downward. The force you exert is upward. Therefore the work you do is negative (force and displacement are in the opposite direction i.e. θ = 180)

5. Oct 19, 2015

### AAAA

Right, sorry! I meant the force is upwards. Yes, I understand now. Thanks!