# Work and Energy

1. Feb 26, 2014

### thomero

1. The problem statement, all variables and given/known data
W = f x D
W = work
f = force
D = distance

What happens when the applied force is not constant?

I have no idea. Can anyone please answer?
Thank you.

2. Feb 26, 2014

### pongo38

Do you know how the force varies with time? Is there a function that expresses this?

3. Feb 26, 2014

### thomero

No. Its just a research question that just ask what happens when the applied force is not constant.

4. Feb 26, 2014

### haruspex

W = F*D is only valid for a constant force and distance measured in the direction in which the force acts. There is a more general equation relating a variable force to distance and work. Properly, it involves calculus and vectors. Not sure what level you're at.
Ignoring the vector aspect, consider the force advancing a small distance ds, so that the force can be taken as not varying enough to matter. Then add up all these contributions over the total distance moved.