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Conservation of energy: Block pulled up frictionless plane

  1. Feb 20, 2008 #1
    1. The problem statement, all variables and given/known data

    A block of mass 3.16 kg, starting from rest, is pulled up a frictionless inclined plane that makes an angle θ = 27.1° with the horizontal by a string parallel to the plane. The tension in the string is 45.8 N. After travelling a distance 2.12 m, the speed of the block is 3.37 m/s. Find the work done by the tension force.

    2. Relevant equations

    [tex]W = KE_{f} - KE_{i}[/tex]

    3. The attempt at a solution

    I came up with:

    [tex]KE_{i} + U_{i} = KE_{f} + U_{f}[/tex]
    [tex]0 + 0 = KE_{f} - U_{f}[/tex]

    so since I am looking to find the final kinetic energy which is equal to work...

    [tex]KE_{f} = -U_{f} = -mgh[/tex]

    but positive because W is positive.

    I got the wrong answer though and I could be way off, could somebody point me on the right track?

  2. jcsd
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