A boy standing on a frictionless ice rink is initially at rest. He throws a snowball in the +x-direction, and it travels on a ballistic trajectory, hitting the ground some distance away. Which of the following is true about the boy while he is in the act of throwing the snowball?
1) He feels an upward force to compensate for the downward trajectory of the snowball.
2) He feels a backward force exerted by the snowball he is throwing.
3) He feels no net force.
4) He feels a forward force, the same force that propels the snowball.
