Physics help, hydraulics and springs?

Question

I know how to do the spring part of this problem, but I'm worried about the distance/height part of the pump. When I got my answer, I didn't account for that because I didn't know how. Is there some way I can take into account the distance that the piston was pushed down or is that impossible with the limited information? Thanks.

http://www.flickr.com/photos/28859420@N07/2752037312/

Answer 1

Sure.

The system in the diagram is in equilibrium, so the net force on each piston is 0.

The fluid levels are the same, so the pressure on the bottom of the two pistons are the same.

You know the weight of the rock and the area of the piston it rests on, so you can determine the pressure.

And you know the area of the left-hand piston so you can determine the force the fluid exerts on it.

That means you know the force exerted by the spring and you are given the spring constant:

force = spring constant x displacement

so you can compute the displacement