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Homework Help: Problem on motions

  1. Sep 25, 2011 #1
    1. A guy with mass m, begins his descent from a diving board 10m high with zero initial velocity.

    (a) Calculate his velocity on impact with the water, v0, and the elapsed time from his jump until impact. Assume there is no air resistance.

    (b) Next under water, let’s suppose the buoyant force on the guy balances his gravitational force and he experiences a viscous force of bv^2. Solve for his velocity v in terms of the depth x under water, taking v=v0 at x=0. (Hint: You’re required to integrate the equation of motion for his vertical descent)

    (c) Suppose b/m = 0.4/m, estimate the depth at which v = 0.1v0.

    (d) Solve for his vertical depth x(t) in terms of the time under water.

    (a) Vf^2 = Vi^2 - 2g (yf-yi)
    V^2 = 0 - 2g (10m)
    V = 9.90m/s
    Vf = Vi - gt
    t = 1.01s
    I only know how to do (a) but I am not sure whether it is right. Please help!!
    Last edited: Sep 25, 2011
  2. jcsd
  3. Sep 25, 2011 #2

    Doc Al

    User Avatar

    Staff: Mentor

    That's the correct formula, but your final answer is incorrect. Double check your arithmetic.
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