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: Question about collisions in 2-dimensions

  1. Feb 21, 2006 #1
    A 0.150 kg billiard ball (A) is rolling toward a stationary billiard ball (B) at 10.0 m/s. After the collision, ball A rolls off at 7.7 m/s at an andle of 40.0 degrees clockwise from its original direction. What is the speed and direction of Ball B after the collision?

    M of A = .150 kg
    M of B = .150 kg
    Vi of B = 10.0 m/s
    Vf of A = 7.7 m/s[70degrees clockwise]

    Vi of A = 0 m/s
    Ff = 0N

    Vi of B = ?

    I started out using the law of conservation of energy but I messed up somewhere early and got fully lost...I know you need to use this method to conserve the momentum of each object but I just can't remember how, can someone start please?
  2. jcsd
  3. Feb 21, 2006 #2
    This is a purely conservation of momentum problem. Pick your x and y axes, initially you have some ammount of momentum in x and y due to the motion of ball A and in the final situation you have the same ammount of momentum in x and y due to the combined motions of A and B.
  4. Feb 21, 2006 #3
    The conservation of momentum

    Last edited: Feb 21, 2006
  5. Feb 21, 2006 #4
    Well, using conservation of momentum should do it. Remember, though, that you should treat the vector components separately, i.e. work it out for a chosen x-direction and y-direction. Easiest would be to have ball A roll in the x-direction.

    EDIT: Wow, the answers keep rolling in. :smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook