1. Not finding help here? Sign up for a free 30min 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!

Elastic collision of a ball

  1. Oct 17, 2006 #1
    Ball #1 moving at a speed of +4.4 m/s along x-axis collides with an identical ball (#2). The initial velocity of ball #2 is equal to zero. Assume that this is a perfectly elastic collision.

    I know that Pbefore = Pafter - but since I'm not given the mass of either ball how am I to know what their velocities are after they hit?
  2. jcsd
  3. Oct 17, 2006 #2
    I have another problem that asks a similar question, no mass given:

    Two balls of equal mass approach the coordinate origin where they collide. Assume that this is a perfectly elastic collision. Before collision, one ball moves along the y-axis at +4.5 m/s and the other ball moves along the x-axis at +4.4 m/s. After they collide, one of the balls moves along the x-axis at +1.2 m/s.

    Find the x-component of velocity of the other ball after the collision =

    How do I get started on these problems? Thanks
  4. Oct 17, 2006 #3
    Identical = equal masses
  5. Oct 17, 2006 #4


    User Avatar
    Homework Helper

    Hint 1: use the facts that momentum and kinetic energy are conserved, if the collision if perfectly elastic.

    Hint 2: when there are more directions, use vectors, and then deal with their components, in order to keep things more clear.
  6. Oct 17, 2006 #5
    ok, for the first question; since they're equal mass and hit directly, total energy is transferred to ball 2. Vball1 = 0, Vball2 = 4.4

    Now, for the second problem I'm supposed to be using vectors to find the x and y components. I will attempt this one later - thanks.
  7. Oct 17, 2006 #6


    User Avatar
    Homework Helper

    Your notation is inconsistent - what exactly do you need to find in 1) ? The velocity of the second ball after the collision?

    Edit. Actually, if the solution is correct, It doesn't matter.
    Last edited: Oct 17, 2006
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Elastic collision of a ball