Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Dropping balls

  1. Feb 15, 2009 #1

    In this problem: http://www.physics.harvard.edu/academics/undergrad/probweek/prob1.pdf [Broken]

    Two balls are dropped, one on top of each other. When figuring out how high the top ball bounces, the solution assumes that the bottom ball hits the ground first, without the other ball on top of it.

    I thought that ideally the two balls would stay on top of each other, since they experience the same acceleration, and would both "hit" at the same time. Is something wrong with my thinking?
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Feb 15, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hello darkSun! :smile:

    No, you're right …

    but it doesn't make any difference to the result if we split the equations into two stages …

    and since that's easier, that's exactly what we do! :wink:

    (technically, of course, the balls deform, and the top of the lower ball doesn't "know" that the bottom has hit the ground until shortly afterwards!)
  4. Feb 15, 2009 #3
    Oh, I see!

    It really doesn't make a difference? Seems weird, but I'll try that.

    Thank you for the help tiny-tim.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook