Question

unit test: forces and motion
a person on a skateboard throws a ball to a friend in front of him. what happens to the skateboard?
the skateboard moves backward a bit.
the skateboard remains in place due to the weight of the rider.
the skateboard moves forward and then backward.
the skateboard moves forward a bit.

Explanation:

According to the law of conservation of momentum, when the person on the skate - board throws the ball forward, an equal and opposite momentum is imparted to the person - skateboard system. So the skateboard moves backward a bit.

Answer:

The skateboard moves backward a bit.