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Impulse and momentum question, relates to Biomechanics

  1. May 11, 2013 #1
    1. The problem statement, all variables and given/known data

    A male and female pair of dancers start dancing when the male lifts the female and throws her into the air. The female's mass is 40kg . The male exerts an average vertical force of 500n for 1.0s on the female.

    What is her vertical velocity when she is released into the air ?


    2. Relevant equations

    I chose to go with Force x Change in time = Mass x Change in Velocity
    FΔt = mΔv



    3. The attempt at a solution

    So I initially came up with

    500N x 1.0s = 40kg x Change in velocity

    (500N x 1.0s)/ 40kg = Change in Velocity

    Change in velocity = 12.5

    The correct answer (if 9.81 m/s is used for g) is 2.69 m/s upwards. I hadn't accounted for g in my answer and am not sure how to incorporate it.
     
  2. jcsd
  3. May 11, 2013 #2

    Doc Al

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    Staff: Mentor

    Is the force that the man exerts on her the only force acting on her?
     
  4. May 11, 2013 #3
    to the best of my knowledge yes, I have literally written out the question as it was presented.
     
  5. May 11, 2013 #4

    Doc Al

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    Staff: Mentor

    Don't forget gravity. (That's where g comes in.)
     
  6. May 11, 2013 #5
    yes this is where I'm confused...how do you incorporate g into it ?
     
  7. May 11, 2013 #6

    Doc Al

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    Staff: Mentor

    There are two forces acting on the woman: The upward push from the man and the downward pull of gravity (her weight). You need to use the net force to calculate her change in velocity.
     
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