Solving Elastic Collision Homework - Exam Prep Question

AI Thread Summary
The discussion revolves around solving an elastic collision problem involving two particles with different masses and initial velocities. Particle A has a mass of 3m and moves with velocity i + 2j, while particle B has a mass of m and moves with velocity -i + j. After the collision, particle A is observed moving along the positive y-axis, prompting the need to find the final speeds of both particles. Participants suggest using conservation of kinetic energy and linear momentum equations to derive the final velocities, with initial attempts focusing on expressing the final velocities in terms of variables. The conversation highlights the challenge of determining the state of particle B after the collision and the need for further calculations based on momentum components.
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Homework Statement


This is an exam prep question

Particle A has mass 3m and velocity i + 2j, it collides with particle B mass m velocity -i + j. Collision is elastic. After collision Particle A is observed to be moving along the +ve y-axis. Find the final speeds of the two particles.(two possible cases)

Homework Equations


Being elastic the kinetic energy is the same before the collision and after.
We are given the answers (3/2,\sqrt{41}/2 or 2,\sqrt{5}.

The Attempt at a Solution


Could someone give me a little nudge in the right direction? I can't see where to begin, what is the state of B after the collision?

Thanks
 
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Right, so you can form the conservation of kinetic energy equation.

You also need to use conservation of linear momentum. Momentum before = momentum after.

Since you do not know the magnitudes of the final velocities, here is how I put them as

vA=λj and vB=αi + βj
 
Thanks for the reply.

I got that far but can't see how to proceed.
 
As rock.freak suggested write up the equations for both the x and y components of the momentum.

ehild
 

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