Conservation of Momentum law problem

  • #1

Homework Statement


m1= 3kg m2= 6kg
v1 = 5m/s v2= 2m/s
d = 3m
DIAGRAM : http://gyazo.com/17b3126726b109256a35f65b86708bb0

Homework Equations


Conservation of momentum:
m1+v1 = m1v1'+m2v2'

Conservation of elastic:
m1v1^2+m2v2^2 = m1v1'^2+m2v2'^2

The Attempt at a Solution


Now my attempt was use both equations & the answers I've gotten so far are 27=3v1'+6v2'(for conservation of momentum) & the 2nd one I've got for the conservation of elastic is 99= 3v1'^2 + 6v2'^2 since they will collide at some point. The only thing I'm stuck at is what to do next afterwards. My teacher has done a similar question but I can never understand how he did it.
 

Answers and Replies

  • #2
105
3
Is the conservattion of momentum law correct ??!
I mean Is it llike what you wrote or like the following
m1v1 + 0 = m1v1+m2v2

Zero indecates that the momentum is zero because the vilocity of the second ball before collision is zero ..
Am I right ..
 
  • #3
105
3
Sorry v1 has a value
so the will be
m1v1 +m2v2 = m1v1+m2v2
 
  • #4
Im just stuck because the example that my teacher gave was like "50=2(10-3v2'/2)^2+3v2'^2" that bracket part confuses me
 
  • #5
105
3
Try to equte the two equation or write v1 in term of v2..
 
  • #6
Try to equte the two equation or write v1 in term of v2..
WOW WHAT THE ****, OK I DID THAT ONE BEFORE. Its this right? " V1+V1' = V2+V2'" but can u explain why that is that cus it made some sense to me. & I showed my friend this process but, she said it made no sense so.
 
  • #7
105
3
I think your teacher has written v1 in term of v2
try to do so from the first equation your v1 will be (27 - 6 v2) /3 which is 9-2v2

It seems reasonable
;)
 
  • #8
I think your teacher has written v1 in term of v2
try to do so from the first equation your v1 will be (27 - 6 v2) /3 which is 9-2v2

It seems reasonable
;)
but why is that though? :( pls
 
  • #9
105
3
Because v1 and v2 are related by these two equations and their value must satisfy both of them
so we make this substitution
I hope that I understand your question and answer it ..
o_O
 
  • #10
Because v1 and v2 are related by these two equations and their value must satisfy both of them
so we make this substitution
I hope that I understand your question and answer it ..
o_O
alright thaanks dawg really appreciate that, last question in the example he gave so the last line was 50-50 = -30v2'+7.5v2'^2
the left side what if it wasnt 0
 
Last edited:
  • #11
105
3
If the lift side isnt zero move it to the right side and solve the quadratic equation..

By the way what does dawg mean in your last comment
o_O
 
  • #12
If the lift side isnt zero move it to the right side and solve the quadratic equation..

By the way what does dawg mean in your last comment
o_O
means like dude lol kids these days
 

Related Threads on Conservation of Momentum law problem

Replies
5
Views
2K
Replies
2
Views
4K
  • Last Post
Replies
1
Views
541
  • Last Post
Replies
1
Views
980
  • Last Post
Replies
4
Views
729
  • Last Post
Replies
4
Views
7K
Replies
1
Views
11K
Replies
11
Views
34K
Replies
2
Views
753
Replies
46
Views
2K
Top