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Homework Help: Force monkey problem

  1. Oct 4, 2015 #1
    1. The problem statement, all variables and given/known data

    A bush baby a small african primate with a mass of 200 grams is capable of leaping vertically to the remarkable height of 2.3m. To jump this high the bush baby accelerates over a distance of 0.16m while rapidly extending its legs . The accelertion during the time the bush baby is pushing off is approximately constant . How much force does the bush baby exert on the ground while it is pushing off ?
    2. Relevant equations
    KE max = GPE max
    1/2m^2=Max Gpe
    impulse = Favrg*t

    3. The attempt at a solution

    well i know that this problem can be solved by using the potential energy and kinetic energy. But our professor assigned this problem while we did not get to this yet. So is there another way to solve this problem let say by using 1st 2nd or 3rd newtons forces laws and kinematics ?
    Last edited: Oct 4, 2015
  2. jcsd
  3. Oct 4, 2015 #2
    It's possible yes. Which part of the question did you use energy for? If it's the height you otherwise know that the maximum height is when the velocity is 0. So you get an equation ##v_0-gt = 0##. After you have ##v_0##(the velocity after acceleration ends) you could calculate the initial acceleration and then the force.

    Edit: I assume this is calculas bases physics, the chain rule comes in handy.
  4. Oct 4, 2015 #3


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    Have you studied the equations of motion? (eg SUVAT).
  5. Oct 4, 2015 #4
    Well the baby obtains the jump by using MAX GPE = mgh
    then set KE max = Gpe max to get intial speed as it leaves the ground
    but i kind get my head twisted when trying to solve it using motion law well tnx for your reply
  6. Oct 4, 2015 #5
    yes we did
  7. Oct 4, 2015 #6


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    Ok so divide the problem into two phases. The launch phase (0 to 0.16m) and the coasting phase (0.16m to 2.3m). Write down what you know about the coasting phase and calculate the required initial velocity.

    Edit: Perhaps "coasting" phase is the wrong term. "Decelerating phase" might be better.
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