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Homework Help: Variable mass of a toboggan down a slope

  1. Oct 22, 2007 #1
    1. The problem statement, all variables and given/known data

    a 5.4kg toboggan carrying 35kg of sand slides from rest down an icy 90m slope inclined at 30 degrees below the horizontal. The sand leaks from the back of the toboggan at a rate of 2.3kgsec^-1. How long does it take the toboggan to reach the bottom of the slope?

    2. Relevant equations
    previous equations involved rockets and the equation:

    v(final) = v(initial) + u ln(mi/mf)
    where u is the exhaust speed

    not sure if this relates to this question though?

    3. The attempt at a solution

    I drew the situation but cant see how to find the time, any suggestions please?
  2. jcsd
  3. Oct 23, 2007 #2


    User Avatar
    Science Advisor

    The rocket equation doesn't apply here. The exhaust speed is zero.
    Apply Fdt=P-P' to your situation.
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