Conservation of momentum and energy problem (Please check if my setup is right)

[Kinermatics]

Homework Statement

Homework Equations

m1v1i + m2v2i = m1v1f + m2v2f (Conservation of momentum)
(1/2)m2*(v2i)^2 + (1/2)m1*(v1i)^2 = (1/2)m2*(v2f)^2 + (1/2)m1*(v1f)^2 (Conservation of energy)

The Attempt at a Solution

I separated the momentum into x and y components and got 2 equations
I used the conservation of energy (can be used since its elastic) and got another equation
-I have 3 unknowns and three equations...which gives me hope that this is solvable lol

Homework Statement

Here are my equations:
Momentum for x:
0 = m2*v2f*sin(theta) + m1*v1f*sin(75)
unknowns here: theta, v2f, v1f

Momentum for y:
m2*v2i = m2*v2f*cos(theta) + m1*v1f*cos(75)
unknowns here: theta, v2f, v1f

Conservation of energy equation:
(1/2)m2*(v2i)^2 = (1/2)m2*(v2f)^2 + (1/2)m1*(v1f)^2
unknowns here: v2f, v1fCan you guys see if these equations are right before I start using the tedious algebra involved in this.

 

[vela]

The x-momentum equation should have a minus sign before the first term, but other than that, your set-up looks fine.

 

[Kinermatics]

oh so..
0 = -m2*v2f*sin(theta) + m1*v1f*sin(75)?
Minus sign just because it goes to the left right?
And thank you!

 

[vela]

Right.

 

[asteriatic]

I can confirm that your setup and equations are correct for solving this conservation of momentum and energy problem. You have correctly identified the unknowns and have set up the equations to solve for them. Good luck with the algebra!