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Homework Help: Football, time in air/distance

  1. Dec 14, 2008 #1
    1. The problem statement, all variables and given/known data
    To get the maximum range, a football kicker kicks a football (at ground level) at an angle of 45degrees. The initial speed of the football is 20 m/s.

    a. How long is the football in the air?
    b. How far up-field does the football hit the ground?


    2. Relevant equations



    3. The attempt at a solution

    Well originally i thought, i must use X=Xo+1/2(V+Vo)t
    to get the time, but that requires X, which is also asked for and not given.
    So then i tried getting X. So i used Rmax= Vo^2/g
    20/9.8=40.8m
    And i also needed V. so i used V^2=V0^2+2a(X-X0)
    and got V=34.6 m/s

    I plugged those in as X and V and got time=1.5 seconds

    However, i only got partial credit, so i don't know where i went wrong
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Dec 14, 2008 #2

    rl.bhat

    User Avatar
    Homework Helper

    Time of flight = 2V_0*sin(theta)/g
     
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