1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Falling Tic-Tac dynamics.

  1. Feb 18, 2012 #1
    Ok, just a few minutes back, a tic-tac slipped from my hand and fell to the ground.

    The second bounce was to a lower height than the first (which is expected because e*<1) but then as it took the third bounce, it rose to a height higher than the one reached by it than in the second bounce.

    I had observed this phenomenon before in pebbles, but today I sat down and started thinking about it, I came up with the following result :

    I noticed (after dropping the tic-tac about a hundred times) that the height of a bounce is higher than the one preceding it only in one particular case : when the tic-tac hits one end on the floor first and then hits the floor a second time before bouncing back.

    To make sense of this, I followed energy conservation.
    The tic-tac originally has a potential energy of mgh and when it bounces back to a new height, it has no transnational kinetic energy, some potential energy and most importantly: Rotational kinetic energy.
    Now to make the tic-tac reach a max height, the rotational kinetic energy would have to be minimum.
    So what actually happens is that when a tic-tac hits the floor a second time in the same cycle, it gets a torque in the opposite direction to what it got in the first hit in the same cycle, hence reducing the rotational and by conservation of energy, making it reach to a higher height.

    That's what I came up with, is it even remotely correct to what is actually going on? Any other thoughts?

    *e = coefficient of restitution
  2. jcsd
  3. Feb 18, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi AlchemistK! :smile:
    Wow, that's amazing … I didn't know you could do that with tic-tacs! :biggrin:

    Yes, that seems a correct analysis.

    I wonder whether there's a similar manouevre in gymnastics?

    I think you should do a few more experiments, and then publish!

    eg, what's the coefficient of restitution for a tic-tac? :wink:
  4. Feb 18, 2012 #3
    I have a counter reasoning too though, since the tic-tac hits for a second time, it looses more energy as heat and sound.

    How do I do that? With all the various uncontrollable variables like friction, angle of drop, and other things, it seems impossible.

    And also, I noticed that the phenomenon occurs more when the tic-tac is dropped at a certain angle, further supporting that the reasoning is correct because the tic tac would only hit twice if dropped at a certain angle.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook