Question

A ball is dropped from the top of a building. If the ball covers a distance of 25 m in the last second of its motion. Find the height of the building and the time taken by the ball to reach the ground (g = 10 m/s2)

Answer 1

Answer:

Explanation:

we know,

s=h=20

a=g=±10m/s=10m/s (since it is dropped)

v^2-u^2= 2as

v^2=2x10x20 (u=0; it is dropped not thrown)

v=20m/s

for calculating time

we know,

v=u+at

20= 0+ 10xt

t=2seconds

thus, it will attain a speed of 20m/s before touching the ground, but the time taken to reach the ground is 2seconds. Because the velocity is not uniform but acceleration/gravity is. If still there is any confusion. Try the same problem with 80 of height.