Question

a boy drops a coin from the top of a tower 50 m high.find the time taken by coin to reach the ground

Answer 1

$s = ut + \frac{1}{2} a {t}^{2} \\ 50 = \frac{1}{2} 10 {t}^{2} \\ t = \sqrt{10}$

Answer 2

S = −40m, u = + 10ms − 1 , a = −10ms −2 Now s = ut + 12at2 => −40 −10t + 12 × (−10)t2 => r2 − 2t − 8 = 0 => (t+2) (t−4) = 0 => t = −2 or 4s

The negative estimation of t isn't conceivable. Thus the ball will hit the ground after 4 s.