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Homework Help: What would happen to the the 5.98e24 kg Earth?

  1. Nov 17, 2007 #1
    1. The problem statement, all variables and given/known data

    If 270 million people in the US jumped in the air at simultaneously, pushing off Earth with an average force of 800 N each for a time of 0.10 seconds, what would happen to the the 5.98e24 kg Earth? Show calculation that justifies your answer.

    2. Relevant equations

    F = mv/t
    p = mv

    3. The attempt at a solution

    F = 800 N
    t = 0.10 s
    m = 5.98e24 kg

    800 = (5.98e24 * v) / 0.10

    v = 1.3378 e -23

    p = 5.98e24 * 1.3378e-23
    p = 80 kg*m/s
  2. jcsd
  3. Nov 18, 2007 #2
    Thats almost right. You forgot the 270 million bit.
  4. Nov 18, 2007 #3
    so do i just times 270 mil by 80?
  5. Nov 18, 2007 #4
    Not quite. F=dp/dt, dp=Fdt. Total change in momentum is zero for the system, therefore,

    This gives p(e)=(270e6)*800*0.1. From this you find the velocity of earth.
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