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Homework Help: Easy question

  1. Sep 23, 2004 #1
    Just a quick question -

    If I throw a ball up in the air, will the velocity be the same coming down as it was going up? Also, will the acceleration change?

    Why does this happen?

  2. jcsd
  3. Sep 23, 2004 #2


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    No, it won't. You said "up in the air", so there will be air resistance slowing it down and it will come down more slowly than it went up. To get the idea, throw a badminton birdie or a feather up as hard as you can. For baseballs, and small thrown heights, however, the difference may not be noticeable.
  4. Sep 23, 2004 #3
    What if you neglect air resistance?
  5. Sep 23, 2004 #4


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    If you neglect air resistance the ball will be at the same speed as it comes past the place where it was released upwards just going in the other direction and the acceleration is still g, 9.8 m/s^2
  6. Sep 23, 2004 #5
    The acceleration doesn't change. I'm assuming that you're still on the surface of the Earth of course.
  7. Sep 23, 2004 #6
    The acceleration due to gravity never changes and is always 9.8 m/s2. Neglecting air resistance, we can therefore reason that the speed of the ball at a certain vertical height when thrown up is the same as its speed at the same vertical height when it falls to earth after being thrown. The velocity, however, changes because the ball is no longer moving in the same direction.
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