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!

Homework Help: Collisions in rotational dynamics

  1. Apr 15, 2014 #1
    If I have say a stationary rod, and a particle collides with the rod whilst moving at speed v at the top end, why does the rod then proceed to rotate about the centre of mass of the system (whether that be in an elastic or completely inelastic collision where they both stick together).

    I believe it may have something to do with the fact the angular momentum can be written as
    with the first term that of a particle with the total mass of the system moving at the CM, and the second the angular momentum of the system relative to the CM (i.e in the CM frame). Thanks.
  2. jcsd
  3. Apr 15, 2014 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    Is that true? If the particle doesn't stick to the rod, why would the rod rotate about the center of mass of the system? Wouldn't it rotate about its own center of mass as it is not interacting with the particle anymore?

    In the case where the two stick together, if they don't rotate about their center of mass, that means the center of mass is rotating about another point, so it is accelerating. Is that consistent with F=ma?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted