A 30-Kg Child Runs at 3

Multiple Choice

A 30-kg child runs at 3.0 m/s and jumps onto a shopping cart and holds on for dear life. The cart has a mass of 20 kg. Assuming the child rides on the cart after the collision, the speed of the child and shopping cart just after the child jumps on is

A) zero.
B) 2.0 m/s.
C) 2.5 m/s.
D) 3.0 m/s.