20. When an object is dropped on a certain earth-like planet, the distance it falls in t seconds, assuming that air resistance is negligible, is given by s(t) = 15t2 where s(t) is in feet. Suppose that a medic's reflex hammer is dropped from a hovering helicopter. Find (a) how far the hammer falls in 3 sec, (b) how fast the hammer is traveling 3 sec after being dropped, and (c) the hammer's acceleration after it has been falling for 3 sec. (@) The hammer falls feet in 3 seconds. (Simplify your answer.) (b) The hammer is traveling ft/sec 3 seconds after being dropped. (Simplify your answer.) (c) The hammer's acceleration is ft/sec/sec after it has been falling for 3 sec. Simplify your