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Homework Help: Intro To Work

  1. Nov 19, 2007 #1
    1. To push a 16 kg crate up a frictionless incline, angled at 15° to the horizontal, a worker exerts a force of 52.8 N, parallel to the incline. As the crate slides 1.50 m, how much work is done on the crate by the worker's applied force? b]

    So I got the first part of this question without any problem. The answer is 79.1 J.

    Its the next part of the question that I'm unsure about:

    How much work is done on the crate by the weight of the crate?

    I tried W=Fg(delta x)
    W=156.8 N (1.5 m)
    W = 235.2 J

    But this obviously isn't right. Where am I going wrong?

  2. jcsd
  3. Nov 19, 2007 #2
    How much of the weight is acting parallel to the plane?
    When you do your FBD mg gets split up into 2 parts, one is perpendicular to the incline, the other is pointed down the incline. You take that portion of the weight * the distance to get the work gravity does.
    Also take direction into account, is gravity opposing the motion or helping move the crate?
  4. Nov 20, 2007 #3
    Is anyone other than me bothered by this question?
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