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.)

convert 200 grams and 100 grams to 2kg and 1kg respectively momentum = mass x velocity momentum = 1 x 2 initial momentum = 2 kg m/ssecond scenario, cart b is moving -.5 m/smomentum = mass x velocitymomentum = 1 x -.5final momentum = -.5 kg m/smomentum has to be the same in both scenarios so the 2 kg truck has to have a momentum of 2.5 kg m/s to push the total momentum of the second scenario to be 2 kg m/s like the first scenario2.5 = 2 x velocityvelocity of cart a after the collision = 1.25 m/s