# Homework Help: Horse power

1. Nov 10, 2006

### jezelee

here is the question...water w/ density 1.0 X 10 (3) kg/m cubed, a well 20 feet deep, and a horse worked for 8 hours. How many liters of water did the horse raise from the well? I am ok in unit conversions, but I need help in figuring out steps in solving this problem.

2. Nov 10, 2006

### Staff: Mentor

What do you think? How much energy does the horse produce in those 8 hours? (Assume its power is 1 horse power. And that all its energy goes into raising water.) And how much energy is required to raise a liter of water 20 feet?

(Be sure to convert to standard units--meters, kilograms, watts, joules.)

3. Nov 10, 2006

### jezelee

First, the depth of the well was meters, not feet. Second, I'm still not sure if I'm heading in the right direction. If water is 1 kg per liter, the work= F dx, and F= ma...then W= (1kg)(9.8 m/s sq.)(20m) = 196 J for each liter rased from the well. correct? If power is W/ dt, and I let the variable n equal the total number of liters raised, I set up an equation of (196)(n)/ 28800 sec = 1Watt. Solving for n gives me ~146.9 liters. Is this correct?

4. Nov 10, 2006

### civil_dude

If my memory is correct, for liquids, P = Q * density * height, where Q is flow in volume/unit time.

5. Nov 10, 2006

### drpizza

You're still missing the horsepower. How many watts is 1 horsepower?