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: Vectors ball of clay physics

  1. Oct 20, 2007 #1
    1. The problem statement, all variables and given/known data

    A 20g ball of clay traveling east of 3.0m/s collides with a 30g ball of clay traveling north at 2.0m/s. What are the speed and the direction of the resulting 50g ball of clay?

    2. Relevant equations



    3. The attempt at a solution

    For most of the other problems in this homework, I've been using m1v1 = m2v2 to find whatever the question asked. I tried using that equation to find v2, but it wasn't right.
     
  2. jcsd
  3. Oct 20, 2007 #2

    learningphysics

    User Avatar
    Homework Helper

    You need to use vectors here...

    split it up into 2 parts... the north/south directions... and east/west directions...

    try to get the north/south velocity of the 50g clay... then the east/west...

    so each part is treated just like the regular one dimensional collisions...
     
  4. Oct 20, 2007 #3
    When you say "vectors" do you mean components? The y-component (north-south) would be vcos(theta)...I think. I can't remember if it's cos or sin.
     
  5. Oct 20, 2007 #4

    learningphysics

    User Avatar
    Homework Helper

    Just call the x-component of the 50g clay... vx. and vy for the north/south part...

    so let's start with the east - west direction.

    initial momentum in the east-west direction = final momentum in the east-west direction.
     
  6. Oct 20, 2007 #5
    Momentum = mv. So (mi)(vi) = (mf)(vf)?
     
  7. Oct 20, 2007 #6

    learningphysics

    User Avatar
    Homework Helper

    Yes exactly... what do you get for vx?
     
  8. Oct 20, 2007 #7
    Ok, so Vx = (.02)(3)/(.05) = 1.2
     
  9. Oct 20, 2007 #8

    learningphysics

    User Avatar
    Homework Helper

    exactly. do the same type of thing to get Vy.
     
  10. Oct 20, 2007 #9
    Vy = (.03)(2)/(.05) = 1.2 also.
     
  11. Oct 20, 2007 #10

    learningphysics

    User Avatar
    Homework Helper

    cool. so now you have vx, vy... you can get the speed and direction...
     
  12. Oct 20, 2007 #11
    I know the direction is 45 degree NE. I tried finding the velocity by using Vx = vcos(theta) and by checking my answer with Vy = vsin(theta). I got .589, but it was wrong.
     
  13. Oct 20, 2007 #12

    learningphysics

    User Avatar
    Homework Helper

    1.2 = v*sin(45)

    solve for v.

    you can also use pythogorean theorem with vx and vy.
     
  14. Oct 20, 2007 #13
    Right. I got 1.697 as the velocity.
     
  15. Oct 20, 2007 #14

    learningphysics

    User Avatar
    Homework Helper

    yup. that's it.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook