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Loss of energy

  1. Oct 9, 2009 #1
    Ok so the rpoblem is A 2.20kg box slides down a rough incline plane from a height h of 1.63m. The box had a speed of 2.33m/s at the top and a speed of 1.90m/s at the bottom. Calculate the mechanical energy lost due to friction (as heat, etc.).

    and im not sure where to even begin with this one. its my last problem I need to finish.
     
  2. jcsd
  3. Oct 9, 2009 #2

    mgb_phys

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    At the top you have kinetic energy and potential energy.
    At the bottom you have kinetic energy.
    The difference is energy lost to friction

    hint work (energy) = force * distance
     
  4. Oct 9, 2009 #3
    So do you do (1/2)mv^2 for both speeds? and find the difference?

    or do you use mgh= PE
     
  5. Oct 9, 2009 #4
    Ok thanks I got it right.
     
  6. Oct 9, 2009 #5

    mgb_phys

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    Both
    do the 1/2 mv^2 for the KE at each end, then take off the 'mgh' the stuff that's left must have gone to friction
     
  7. Oct 9, 2009 #6
    Yeah I got it. mgh is PE and .5mv^2 is KE at the top then you have .5mv^2 at the bottom and find the difference. got 3.72e+01 J. and it was right.
     
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