physics

boy throws a penny into an empty well with an initial velocity of –2 m/s. He hears it hit the bottom 8 seconds later. About how far did the penny fall?

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asked by Anonymous
  1. t'=time to fall
    t"=time for sound to return after bottom

    t'+t"=8

    depth=2*t'+1/2 g t'^2
    depth=velocitysound*t"

    set them equal (same depth)

    2*t'+1/2 g t'^2=velocitysound*t"
    2*t'+1/2 g t'^2=velocitysound*(8-t')

    so solve for t', and then you can get depth.

    posted by bobpursley

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