1. Not finding help here? Sign up for a free 30min 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!

Law of Conservation of Energy

  1. Dec 6, 2003 #1
    A skier of mass 55.0 kg slides down a slope 11.7 m long, inclined at an angle theta to the horizontal. The magnitude of the kinetic friction is 41.5 N. The skier's initial speed is 65.7 cm/s and the speed at the obttom of the slope is 7.19 m/s. Determine the angle theta from the law of conservation of energy. Air reistance is negligible.

    The answer is 17.5 degrees, but the work is hard for me to start at.
    From what I've learned, we use Et1 = Et2, and I can find theta from 11.7 sin theta which is delta y. I get 12.9 degrees from this. I know this is incorrect, and the friction force needs to be added in somewhere, I just don't know where.
     
  2. jcsd
  3. Dec 7, 2003 #2

    Doc Al

    User Avatar

    Staff: Mentor

    If it wasn't for friction, the mechanical energy (KE + PE) would be conserved. The change in KE + PE (a decrease, of course) is equal to the work done by friction on the skier. (Don't forget that work is negative if the force is opposite the displacement.)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Law of Conservation of Energy
Loading...