A girl hits a baseball with a bat. When the bat strikes the ball, what is the reaction force?
A. Earth's gravity pulls the ball down.
B. The ball accelerates upward.
C. The bat pushes against the girl's hands.
D. The ball pushes against the bat.

Aballoon is rising vertically upwards at a velocity of 10m/s. when it is at a height of 45m from the ground, a parachute bails out from it. after 3s he opens his parachute and decelerates ata a constant rate 5m/s.when. (a) what was the height of the parachutist above the ground when he opened his parachute? (b)how far is the parachutist from the balloon at t=3s? (c)with what velocity does the parachutist hit the ground? (d)after how long does the parachutist hit the ground after his exist from the balloon?