Physics
posted by Maria on .
On a planet that has no atmosphere, a rocket 14.2 m tall is resting on its launch pad. Freefall acceleration on the planet is 4.45 m/s2. A ball is dropped from the top of the rocket with zero initial velocity. (a) How long does it take to reach the launch pad? (b) What is the speed of the ball just before it reaches the ground?

a. d = 0.5gt^2,
14.2 = 0.5 * 4.45 * t^2,
14.2 = 2.225t^2,
t^2 = 14.2 / 2.225 = 6.38,
t = sqrt(6.38) = 2.53 s.
b. V^2 = 2gd,
V^2 = 2 * 4.45 * 14.2 = 126.4,
V = sqrt(126.4) = 11.2 m/s.