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Balloon and ballast

  1. Apr 15, 2016 #1
    1. The problem statement, all variables and given/known data

    A balloon is ascending at an speed of 13 m/s. At 300 m from the ground a ballast is drop from the balloon. Find the maximum height the ballast reach.

    My doubt is: When the ballast is drop ¿it starts falling inmediately?. The solution of the problem implies that the ballast keep ascending for 8,6 m.

  2. jcsd
  3. Apr 15, 2016 #2


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    While the balloon is ascending, everything in the balloon is ascending at the same velocity. It's no different if you pick up a rock and throw it straight up at 13 m/s.

    It takes gravity a finite duration to arrest the upward motion and bring the velocity to zero, before things begin to fall back to the ground.
  4. Apr 15, 2016 #3
    An observer in the ground would see the ballast fall inmediately, I mean he wouldn't see the ballast ascending for 8,6 meters. That's what I imagine. What's wrong with my imagination?
  5. Apr 15, 2016 #4


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    What about a ball dropped from a car moving at 13 m/s?
    If you're watching from the side of the road what speed will the ball be travelling as soon as it's dropped? Will it s stop where it lands? Or continue bouncing down the road?
  6. Apr 15, 2016 #5


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    How do you know what someone else sees?

    If you throw a rock straight up at 13 m/s, does the rock stop immediately once it leaves your hand and drop to the ground?

    You can imagine many different things, some real, some impossible. We deal with science at PF, not your imagination.
  7. Apr 15, 2016 #6
    This is a great example. Thanks.
  8. Apr 15, 2016 #7
    Sure not. The observer in the ground just can't note the ballast keep ascending because of the distance and he has no reference to compare the movement (the clouds are not good ones). An observer at the same level when the ballast is drop, would see the ballast ascending a little.
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