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: Question related to energy

  1. Nov 1, 2003 #1
    here is a question that I am unable to solve:

    The average human, of mass 52 kg needs to have approximately 9,000,000 J of energy per day. Suppose, you had to walk up a hill with an incline of 12 degrees. Determine the following:
    a) how high would the hill have to be (i.e. - change in height) in order to consume all of this energy.
    b) how much work did gravity do in all of this walking?

    for A, i know you have to use the formula Eg=mgh but i am not sure where to sub in the energy as 9,000,000J or sin 12*9,000,000 (since its at an angle)

    B) i dont knoe what role gravity plays in this?
  2. jcsd
  3. Nov 1, 2003 #2
    In the formula mgh, h refers to just the vertical displacement, not the total distance.

    For the work, you need to consider the definition of work done by a force (in this case, gravity) -- or, equivalently (in this case), the work done by changing potential energy.
  4. Nov 1, 2003 #3
    Re: Re: question related to energy

    sorry, but you haven't answered my question? directly
  5. Nov 1, 2003 #4
    Re: Re: Re: question related to energy

    Energy is energy. You don't multiply it by anything.
  6. Nov 1, 2003 #5
    SO, energy is not a vector quantity?
  7. Nov 1, 2003 #6
    No, energy is a scalar.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook