Two carts collide on a level, friction-less track. Cart A has a mass of 200 g and is initially stationary. Cart B has a mass of 100 g and is initially moving with a velocity of +2.0 m/s. After the collision between the carts, cart B has a velocity of -0.5 m/s.
Calculate the velocity of cart A after the collision.
(Use conservation of momentum, KE is not conserved.)