Question

A man fires a rock out of a slingshot directly upwards the rock has an initial velocity of 15m/s
What is the maximum height that the rock will reach

Answer 1

Fdown = m g
so a = - g = -9.81 m/s^2
so
v = -9.81 t + Vi = -9.81 t + 15
v = 0 at top
so
9.81 t = 15
t = 1.53 seconds upward
h = (1/2) a t^2 + Vi t + Hi = -4.9 t^2 + 15t = -11.5 + 23 = 11.5 meters
or if you know loss of Ke = gain in PE
(1/2) m v^2 = m g h
(1/2)(225) = 9.81 h
h = 11.5 meters again