Question abot solving final velocity in elastic collision

AI Thread Summary
In an elastic collision problem involving a 0.25 kg ball and a 0.21 kg ball, the conservation of kinetic energy and momentum are key principles to solve for the final velocities after the collision. The potential energy of the raised ball converts to kinetic energy at the bottom of its swing, providing the initial velocity for the collision. Two equations are established: one for energy conservation and another for momentum conservation. By solving these two equations simultaneously, the final velocities of both balls can be determined. The discussion emphasizes the importance of understanding the frame of reference in this context.
HelloMotto
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A 0.25 kg ball is attached to a 26-cm piece of string. The ball is first raised so that the string is taut and horizontal, then the ball is released so that, at the bottom of its swing, it undergoes an elastic headon collision with a 0.21 -kg ball that is free to roll along a horizontal table. Find the velocity of each ball after collision.

since its elastic i know Ke is conserved as well as momenta. So i have 2 equations.
Im not sure what to do with those 2 equations to get the final velocities of each ball.
My teacher said something about frame of reference.
 
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HelloMotto said:
A 0.25 kg ball is attached to a 26-cm piece of string. The ball is first raised so that the string is taut and horizontal, then the ball is released so that, at the bottom of its swing, it undergoes an elastic headon collision with a 0.21 -kg ball that is free to roll along a horizontal table. Find the velocity of each ball after collision.

since its elastic i know Ke is conserved as well as momenta. So i have 2 equations.
Im not sure what to do with those 2 equations to get the final velocities of each ball.
My teacher said something about frame of reference.

The only thing you are missing are the 2 final velocities.

You have 2 equations: 1) expressing the potential energy of the ball at release as the sum of the final KE's and 2) Knowing the initial V at impact you know what the sum of the final momentum must be.

2 equations + 2 unknowns = Solution
 
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