• Support PF! Buy your school textbooks, materials and every day products Here!

Prooving Elastic Collisions equations

  • Thread starter Lord Dark
  • Start date
  • #1
121
0

Homework Statement


hi everyone ,, how are you all ? ,, i have these two equations and i don't know how to get them :
v1f=((m1-m2)/(m1+m2))*v1i +(2m2/(m1+m2))*v2i
V2f=((2m1/m1+m2))*v1i+((m2-m1)/(m1+m2))*v2i


Homework Equations


m1v1i+m2v2i=m1v1f+m2v2f (conservation of momentum)
0.5m1v1^2i+0.5m2v2i^2=0.5m1v1f^2+0.5m2v2f^2 (conservation of Kinetic Energy)


The Attempt at a Solution


the book reach to taking m1 & m2 as common factor then says divide the kinetic by the momentum then I'll get the results above, but when i divide i get :
v2f=v1i+v1f ,, so someone help me to get the results above because i don't like memorizing and i know that I'll forget in the exam -_-
 

Answers and Replies

  • #2
rl.bhat
Homework Helper
4,433
5
m1v1i+m2v2i=m1v1f+m2v2f (conservation of momentum)
0.5m1v1^2i+0.5m2v2i^2=0.5m1v1f^2+0.5m2v2f^2 (conservation of Kinetic Energy)

In both the equations collect the terms containing m1 on one side and m2 on other side. Then divide left hand side and right hand side and equate. You will get relation between v1i, v1f ,v2i and v2f. Using this you can find the required result.
 

Related Threads for: Prooving Elastic Collisions equations

  • Last Post
Replies
18
Views
1K
Replies
4
Views
1K
Replies
3
Views
4K
  • Last Post
Replies
2
Views
3K
Replies
23
Views
9K
  • Last Post
Replies
1
Views
5K
Replies
14
Views
3K
  • Last Post
Replies
4
Views
2K
Top