An air track cart with mass m 0.4kg and initial speed v0 = 0.7m/s collides with and sticks to a second cart that is at rest initially. If the mass of the second cart is m2 = 0.5kg, how much kinetic energy is lost as result of the collision?

Answer 1

initial KE ... 1/2 * .4 * .7^2

momentum is conserved
... .4 * .7 = (.4 + .5) * v

solve for v

final KE ... 1/2 * (.4 + .5) * v^2

Answer 2

im still confused