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: Help! elastic head-on collision

  1. Dec 7, 2005 #1
    a 3.42g object moving to the right at 16.4 cm/s makes an elastic head-on collision with a 6.84g object that is initially at rest. find the velocity of the first object immediately after collision. Answer in units of cm/s. What fraction of the initial kinetic energy is transferred to the 6.84g object?

    I dont understand how to do this problem. I think for the first part is it
    M1v1i+M2V2i=M1V1f+M2V2f
    and im lost after that. I completely dont get part 2
     
  2. jcsd
  3. Dec 7, 2005 #2

    NateTG

    User Avatar
    Science Advisor
    Homework Helper

    Indeed, you have:
    [tex]P_{\rm{initial}}=P_{\rm{final}}[/itex]
    which gives you one equation.

    But, you have two unknowns ([itex]v_1[/itex] and [itex]v_2[/itex]), so you'll need another equation. What do you know about elastic collisions?
     
  4. Dec 7, 2005 #3
    energy and momentum is conserved in elastic collisions?
     
  5. Dec 7, 2005 #4

    NateTG

    User Avatar
    Science Advisor
    Homework Helper

    Right. The equation you have listed only deals with momentum.
     
  6. Dec 7, 2005 #5
    hmm i still dont get it
     
  7. Dec 7, 2005 #6

    NateTG

    User Avatar
    Science Advisor
    Homework Helper

    Can you write expressions for the total kinetic energy before and after the collision?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook