1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Horse power

  1. Nov 10, 2006 #1
    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. jcsd
  3. Nov 10, 2006 #2

    Doc Al

    User Avatar

    Staff: Mentor

    What do you think? How much energy does the horse produce in those 8 hours? (Assume its power is 1 horse power. :wink: 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.)
  4. Nov 10, 2006 #3
    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?
  5. Nov 10, 2006 #4
    If my memory is correct, for liquids, P = Q * density * height, where Q is flow in volume/unit time.
  6. Nov 10, 2006 #5
    You're still missing the horsepower. How many watts is 1 horsepower?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook