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

Inelastic Collision

  • Thread starter kk727
  • Start date
  • #1
54
0

Homework Statement



2ur1lwy.png


Ball 1: 3kg, 7 m/s initially
Ball 2: 4kg, V m/s initially
Ball 3: 5kg, 10 m/s initially

Find V if the system collides inelastically and moves off at 2 m/s at 5 degrees above the horizontal.

Homework Equations



p + p = p + p (in both x and y directions)

The Attempt at a Solution



I set up the equations for momentum in both directions (sin and cosine). I ended up with 4v*sinθ = 13.7558 and 4v*cosθ = 50.608. I then solved for θ and got 15.2 degrees and an initial velocity for Ball 2 of 13.11 m/s. I don't believe this is the answer my teacher had in class.

My only question is, when setting up the problem, would you consider the velocity of Ball 3 to be negative? That's how I calculated it. I have no problems with the calculations, just the setting up of the problem. I didn't write all of my work down, but it was something like this:

(sin 15)(7)(3) + (sin θ)(v)(4) + (5)(-10)(sin 20) = (2)(sin5)(12)

And I simplified it, did the same for cosines, solved for θ, and then plugged in to solve for V.

Am I way off?

:/
 

Answers and Replies

  • #2
Delphi51
Homework Helper
3,407
10
(sin 15)(7)(3) should be negative, too - the vertical component is down.
 
  • #3
54
0
Thank you! I realized I had my signs all wrong...stupid mistake! I figured it out and got the right answer!
 

Related Threads on Inelastic Collision

Replies
2
Views
3K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
5
Views
748
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
605
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
0
Views
847
  • Last Post
Replies
3
Views
3K
  • Last Post
Replies
7
Views
3K
  • Last Post
Replies
2
Views
2K
Top