Two young sisters with a combined mass of 75 kg ride on a cart of mass 30.0kg travelling at 2.0 m/s. If they jump off together so they land with zero speed relative to the ground, what is the change in speed of the cart?

Answer 1

Initial momentum=finalmomentum
(2*75+30)2.0=2*75*0+ 30v
solve for velocity v.
then the change is speed is v-2.0

Answer 2

thank you !

Answer 3

Wrong! The answer has to be 7 m/s. Its just reverse logic. M1Vc + M2Vc = M1V1 + M2V2.
Vc = 2, V1 = 0 (assuming it starts from rest), V2 = unknown, and thats what you are finding.

Answer 4

M1 = 75, M2 = 30