Tuesday, December 22, 2009

If you dropped a super ball from cruising altitude (between 2 and 3,000 feet) how high the resuting bounce would be
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2 comments:

  1. MarkleDecember 23, 2009 at 3:39 PM

    The super ball would probably reach terminal velocity by the time it hit the ground*. One of my quick-and-dirty 'net searches says that super balls lose about 85% of their energy every bounce.

    So, given a whole mess of assumptions that I can go over if you like, I'm going to say it will only bounce back to a height of 267 feet, no matter whether it is dropped from 2000 or 3000 feet.

    'Course, personally, I doubt it would survive its 40 m/s collision with the ground: it probably wouldn't bounce back up at all.

    This is a fairly complicated problem if you include air resistance. If not, then it is fairly simple.

    *Terminal velocity for a light, smooth 2-inch-diameter ball is about 40 m/s. If we had ignored air resistance, it would have reached between 117 and 134 m/s, depending on the height it was dropped from.

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  2. Michael BakerDecember 25, 2009 at 5:21 PM

    Let's have some fun in happy-go-lucky physics land and throw air resistance out the window.

    Let's pull a number out of thin air, let's say on the rebound, it'll go 75% of it's original height. Having spent a childhood dropping superballs off of second-story balconies (you and me both, sara) that should be an acceptable figure.

    Applying that 75% figure to 2000ft gets us 1,500ft, whereas applying that 75% figure to 3000ft gets us 2,250ft. Add the two and average them out and you get 1,875ft on the first rebound.

    Though Markle's method is more complete, especially if she (she? is markle a she? I don't actually know) were to figure what the ball's weight was so she could figure how much energy it would have just before impacting the ground.

    But Markle is completely correct in assuming the ball wouldn't survive it's trip downward. When Robotics went to Atlanta, one of us dropped a superball down the atrium of the hotel from the 46th floor, and upon impact with the lobby floor, it broke, sending rubber bits everywhere. And that was from a few hundered feet (I can't recall exactly how tall, though we did the math and figured out how much kinetic energy that ball had before impact), nevermind a few thousand.

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