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## Homework Statement

On a frictionless, horizontal air table, puck

*A*(with mass 0.250 kg ) is moving toward puck

*B*(with mass 0.360 kg ), that is initially at rest. After the collision, puck

*A*has a velocity of 0.125 m/s to the left, and puck

*B*has velocity 0.655 m/s to the right.

I already solved for the puck's initial velocity, which is 0.818m/s. Now I have to find the change in the total kinetic energy of the system that occurs during the collision.

## Homework Equations

KE=(1/2)mv^2

## The Attempt at a Solution

KE(initial)=(1/2)(0.250kg)(0.818m/s)^2=0.0805J

KE(final)=(1/2)(0.250kg)(0.125m/s)^2+(1/2)(0.360kg)(0.655m/s)^2=0.07917

ΔK=0.0805J-0.07917J=0.00487J.

I tried this both negative and positive, but both are wrong. I don't know what I did wrong.