Question

a stone is thrown vertically upward with an initial velocity of 14m/sc negleting in air resistance find (a)Maximum height reached and (b)Time taken before it reached the ground ​

Answer 1

1/2 m v^2 = m g H conservation of energy

H = (v^2 / (2 * g))^1/2 = (14^2 / 19.6)^1/2 = 10 m

H = 1/2 g t^2 time to fall 10 m

t = (2 * H / g)^1/2 = (20 / 9.8)^1/2 = 1.43 sec

Total time in air = 2 * 1.43 = 2.86

You can also use 2 a S = V0^2 since final velocity = 1.43 * 9.8 m/s = 14 m / s

and 2 a S = 2 * 9.8 * 10 = 196 m^2 / s^2 which is V0 squared