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Homework Help: Projectile; centre on gravity

  1. Sep 1, 2011 #1
    1. The problem statement, all variables and given/known data
    A jumper takes off with a velocity of 5 ms at an angle of 20 degrees to the horizontal.
    How high does he raise his center of gravity?

    2. Relevant equations

    3. The attempt at a solution
    I know that Vh= 5scos20 = 1.7 m/s and Vv=5Csin20=4.70 m/s

    using 0=Vi^2 + 2ad
    0=5sin20 + 2 X-9.81d
    d=0.087m, but its incorrect. Am I misssing something? The only Thing I can think of is beacuse its his centre of gravity that I should treat it as a vertical launnched projectile?
    Last edited: Sep 1, 2011
  2. jcsd
  3. Sep 1, 2011 #2


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    Homework Helper

    Nothing wrong with your calculation. Since they are asking how high, could this be the high-jump and the angle is actually 20 degrees to the vertical?
  4. Sep 1, 2011 #3
    thanks for your help, thats what i was thinking would it then mean that the Vv is 5Cos20 instead of 5Sin20? Is that what you are suggesting?, also the answer is 0.14m...
  5. Sep 1, 2011 #4
    Can anyone else help... I still cant get 0.14m???

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