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Homework Help: Calculating speed in water taking drag force into account

  1. Oct 16, 2008 #1
    1. The problem statement, all variables and given/known data

    You dive straight down into a pool of water. You hit the water with a speed of 6.5 m/s, and your mass is 75 kg. Assuming a drag force of the form Fd = (−1.00×104 kg/s) v, how long does it take you to reach 2% of your original speed? (Ignore any effects of buoyancy.)

    2. Relevant equations


    3. The attempt at a solution

    no ideas whatsoever
  2. jcsd
  3. Oct 21, 2008 #2
    First, write down Newton's second law. On one side we have acceleration, which is the first derivative of velocity, and on the other side, we have velocity, so this is a differential equation. (Don't forget about gravity.) Solve this differential equation to get velocity as a function of time. This should get you started.
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