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: Help me? lol

  1. Feb 21, 2010 #1
    1. The problem statement, all variables and given/known data

    You and your friend Peter are putting new shingles on a roof pitched at 23degree . You're sitting on the very top of the roof when Peter, who is at the edge of the roof directly below you, 5.4 m away, asks you for the box of nails. Rather than carry the 2.3 kg box of nails down to Peter, you decide to give the box a push and have it slide down to him.
    If the coefficient of kinetic friction between the box and the roof is 0.50, with what speed should you push the box to have it gently come to rest right at the edge of the roof?

    2. Relevant equations
    I dont know lol

    3. The attempt at a solution
    so I drew the free body diagram but I really dont know where to go from there. I think the problem is i just dont know which equations to use. any help is appreciated
  2. jcsd
  3. Feb 21, 2010 #2
    Use energies. It starts out with energy that carries it down the roof and stops at the bottom with zero final energy. There was work down on it to change the energy, frictional work.

    W = Delta KE
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook