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Homework Help: Physics-dynamics question with incline?

  1. Mar 14, 2010 #1
    No matter how many times i do it, i seem to be doing something wrong :|

    1. The problem statement, all variables and given/known data
    A wet bar of soap (150 g) slides without friction down a ramp (2.0 m) long inclined at 7.3degrees. How long does it take to reach the bottom? Neglect friction.
    & How would this change if the soaps mass were 250 grams?

    2. Relevant equations

    stated below>>

    3. The attempt at a solution
    So i tried to calculate Fnet using sine.
    since Fg=1.5kg*9.8=14.7N
    Then i did, sin7.3=x(aka fnet) / 14.7
    x = 12.5

    Then: Fnet = ma

    t=0.219 or around there.

    However the answer is 1.8 seconds?
    Can anyone help me see what im going wrong?

    Any help is much appreciated, thanks.

    Sorry, nevermind, turns out my calc was in radian mode -facepalm- Good grief.
    Last edited: Mar 14, 2010
  2. jcsd
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