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: Rank the velocities of the balls

  1. Oct 15, 2012 #1
    1. The problem statement, all variables and given/known data Small masses m1 (m1 = 30 kg) and m2 (m2A = 5 kg; m2B = 10 kg; m2C = 40 kg; m2D = 50 kg; m2E = 30 kg) are each attached to a string of length 2.0 m. The other end of each string is attached to a common point on the ceiling. The masses are raised until each string is at an angle of 22o with respect to vertical, and then simultaneously released. They collide elastically when the strings are vertical. For each case, rank the final velocity of m2, from smallest to largest.

    2. Relevant equations using the elastic equation formula

    3. The attempt at a solution i don't understand y the heaviest one wouldn't be going the fastest.....
  2. jcsd
  3. Oct 15, 2012 #2
    You just need to write generic equations for an elastic collision and then plug in the masses for each case.
  4. Oct 16, 2012 #3
    The heaviest one is the one most difficult to influence - whereas the lightest one is the easiest. Or what happens if you roll 2 marbles of different weights together?

    I think this assignment has to do with the law of conservation of momentum.

    If you release all the balls at an angle, by the time they're about to collide, the system has a total momentum of 0, and after the collision has happened it will need to stay that way.
  5. Oct 16, 2012 #4
    oh ok I see that analogy explains it better....i will work on that and see what I get. thanks
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook