Question

A 35 kg girl on roller skates, standing still
throws a 6 kg medicine ball forward at 3
metes per second. How much is her recoil
velocity (the backward speed she acquires as
a result of the throw)?
(1) 0.6 m/s
(2)-1.6 m/s
(3)-2.6 m/s
(4)-5.6 m/s
​

Answer 1

The answer is (1)

Based on the law of conservation of momentum.