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Work problem

  1. Feb 24, 2004 #1
    I have question regarding work and I was stuck with the wrong solutions.

    A guy slides a crate up a ramp at angle of 27 deg. by exerting a 285 N force parallet to the ramp. The crate moves at a constant spped. The coefficient of friction is 0.23. How much work did this guy do when the crate was raised a vertical distance of 1.27 m?

    I started with constant speep. It means that the force 285 N = mg*sin27 + mgcos27*0.23

    m = 44.13 kg.

    delta U = 44.13 * 9.8 * 1.27 = 549 J

    W = - delta U = - 549 J.

    The answer was wrong. Can anyone help. Thanks in advance.
  2. jcsd
  3. Feb 24, 2004 #2
    Thanks, I got

    I just figured out that I should have used W = F * D since it is moving at constant speed. The combination of friction and gravity force will be equal to the F. That's all he need to move to move crate up.

    The answer is 797.26 J
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