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## Homework Statement

*3. Water is pumped from one reservoir to another 100m away. The water level in the second reservoir is 20m above the water level of the first reservoir. What is the increase in specific potential energy of the water in J/kg?*

## Homework Equations

The relevant equation I've been given in my notes is

P = mgh

This problem is for a renewable energy course. In class I only received a definition of potential energy and the above equation, the teacher didn't do any problems with potential energy in class either. The given textbook doesn't touch on the quantitative side of renewable energies. I've been trying to look through old physics textbooks but can't find anything too helpful yet.

## The Attempt at a Solution

I have been away from physics for almost 8 years, so physics problems aren't very intuitive for me anymore.

So far I've assumed I'm calculating the change in P. Setting up the equation as :

*ΔP = (mgh)2nd reservoir - (mgh)1st reservoir*

with

Δ (mass*g) = (20m* ? * density of water)*9.8m^2/sec

Δh = 100m

I can't figure out how to get the Δ in the volume of water, which I need to get the mass. Or since the teacher wants the answer in J/kg, should I be assuming that I should set up the equation as:

ΔP/m = Δ(g*h) ?

Any help would be great.

Thanks,

Alyssa

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