Question

A ball dropped freely takes 0.2 seconds to cross the last 6 m distance before hitting the ground. total time of fall is ? ( g =10m/s^{2 )}

^2.9s

^3.1s

^2.7s

^0.2s

Answer 1

Height = H

Total time = T

H = 0.5gT^2

H - 6 = 0.5g(T - 0.2)^2

0.5gT^2 - 6 = 0.5g(T^2 + 0.04 - 0.4T)

0.5gT^2 - 6 = 0.5gT^2 + 0.02g - 0.2gT

-6 = 0.02g - 0.2gT

T = (0.02g + 6) / (0.2g)

T = [(0.02 * 10) + 6) / (0.2 * 10)

T = 3.1 s