Answer units Question 18 (11 points) A stone is thrown horizontally at 28.0 m/s from the edge of a cliff. The stone lands 46.0 m from the base of the cliff. Determine the time the ball was in the air. Your Answer: Answer units Question 19 (11 points) Saved A centrifuge accelerates from rest to 12,000 rpm in 350 s. How many revolutions did the centrifuge complete during its 350 s spin-up? Your Answer: rev Answer units Question 20 (11 points) What constant force is needed to stop a 1,600-kg car in 8.00 s if it is traveling at 52.0 m/s