A 57 g tennis ball is traveling at 45 m/s to the right, when it hits a racket. The ball reverses direction and travels at 33 m/s. The ball is in contact with the racket for 0.0085 s.

What is the magnitude of the force that was exerted on the ball?

Ahot-air balloon takes off from the ground traveling vertically with a constant upward acceleration of magnitude g/4. after time interval δt, a crew member releases a ballast sandbag from the basket attached to the balloon. how many seconds does it take the sandbag to reach the ground? (express your answer in terms of δt)