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Homework Help: A Child throws a ball vertically upwards, then catches it

  1. Mar 14, 2015 #1
    1. The problem statement, all variables and given/known data
    Taking the intial velocity to be 10.0 m/s, g to be 9.8m/s2 and ignoring effects of air calculate:
    -the total time of flight of the ball
    -the maximum height it reaches

    2. Relevant equations

    3. The attempt at a solution
    I've recently switched to Physics at school and I'm unsure about this question. Why isn't the intial velocity zero if it is being thrown up?
  2. jcsd
  3. Mar 15, 2015 #2


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    Because the problem says the initial velocity upward is 10m/s. Why do you think it should be zero?
  4. Mar 15, 2015 #3


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    Take your hand and pick up a ball.
    Turn your hand over, so that the ball is resting in your palm.
    Relax your fingers.
    This is a ball with a zero vertical velocity. :wink:
  5. Mar 15, 2015 #4


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    When problems about trajectories refer to initial and final velocities, they mean the initial and final velocities while in the air. The velocity whilst still in the hand or after hitting the ground are not apropriate because in those phases there are forces other than gravity (and air resistance) acting.
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