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On a frictionless, horizontal air table, puck A (with mass [tex]m_1[/tex]) is moving toward puck B (with mass [tex]m_2[/tex]), that is initially at rest. After the collision, puck A has a velocity of [tex]v_1[/tex] to the left, and puck B has velocity [tex]v_2[/tex] to the right.

1.What was the speed of puck A before the collision?

My answer to this part of the question was correct. It is [tex](m_2*v_2)/(m_1) - (v_1)[/tex].

2.Calculate the change in the total kinetic energy of the system that occurs during the collision.

I think this depends on the first part of the question.

So, I'm thinking:

[tex]\Delta K= K_f - K_i[/tex]

[tex](1/2)(m)(v_f^2 - v_i^2)[/tex]

I should sum up the velocities, right?

[tex](1/2)(m_1+m_2)((v_2 - v_1)^2 - ((m_2*v_2)/(m_1) - (v_1))^2)[/tex]

But, that is not correct.

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# Homework Help: Change in total kinetic energy in a conservation of momentum problem?

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