The absence of air resistance
28. (a) In the absence of air resistance, what is the change in velocity for an object that has fallen for 4.0 s?
(b) An arrow is shot straight up with an initial velocity of 45 m/s. What is the velocity of
the arrow after 2.5 s?
(c) A rock falls from the top of a high cliff. How long would it take this rock to reach a
velocity of 25 m/s downward?