Question

A ball is dropped freely under gravity from the top of a tower of height 78.4 m. (4)
Calculate:
(i) the time to reach the ground, and
(ii) the velocity with which it strikes the ground.
Take g = 9.8 ms-2
.

Answer 1

Answer:

time taken =4 sec

final velocity= 39.2 m/s

Explanation:

Height(h)=78.4m, g=9.8m/s²

initial velocity(u)=0m/s

final velocity=v m/s, time taken = t sec

i) time taken

h=ut +1/2 gt²

=>78.4=0+1/2 (9.8)t²

=>t²=(78.4×2)/9.8

=>t=√(16) sec=4 sec

ii) final velocity

v=u+ at

v=0 + 4×9.8= 39.2 m/s