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Homework Help: So confused! please help! Kinematics in one dimension

  1. Sep 11, 2008 #1
    A hot air balloon is ascending straight up at a constant speed of 8.80 m/s. When the balloon is 12.0 m above the ground, a gun fires a pellet straight up from ground level with an initial speed of 31.0 m/s. Along the paths of the balloon and the pellet, there are two places where each of them has the same altitude at the same time. How far above ground level are these places?

    I got 0.628 and 3.90 for my answers and they're wrong! I dont know what I did but I cant find what I did wrong! help please!
  2. jcsd
  3. Sep 11, 2008 #2
    how do you get 0.628 and 3.90 .show us
  4. Sep 11, 2008 #3
    oh i got the answer! I used this equation and used the quadratic formula:

    -4.9t^2+t(Velocity of pellet gun-velocity of balloon)-12=0
    then plugged those two answers into the following as is:

    0.628 into distance of balloon=12+speed(0.628)= 17.5 m
    and distance of pellet=initial speed(3.9)-((9.8(3.9^2))/2)= 46.4 m
  5. Sep 11, 2008 #4
    Inorder to know where those meet in the same hight you have to make equall

    like pellet = gun
    and you have to solve as you did above
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