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Newton's Laws

  1. Mar 19, 2009 #1
    1. The problem statement, all variables and given/known data

    A 100 kg block is pulled at a constant speed of 3 m/s across a horizontal floor by an applied foce of 145 N directed 37 degrees above the horizontal. What is the rate at which the force does work on the block? _____ W

    2. Relevant equations
    work = force (dot product) displacement
    work = .5m * v^2 (final) - .5m *v^2 (initial)

    3. The attempt at a solution

    i used the second equation and plugged in my mass as 100kg and my final velocity as 3. so i got .5(100)(3^2) = 450 W. That seems like an awful lot to me ????
  2. jcsd
  3. Mar 19, 2009 #2
    Its the rate at which force does work.
    What is the rate at which work is done known as?
  4. Mar 19, 2009 #3
    Is it power?
  5. Mar 19, 2009 #4
    This is something else I've tried.

    Power = work / time = force (dot product) displacement = force * average velocity * cos(37 desgrees). I cam out with 347. 41 W. Am I doing this correctly?
  6. Mar 19, 2009 #5
    Solved. Thanks for jogging my memory!!
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