Question

A ball is thrown vertically upwards with a velocity of 20 ms from the top
of a multi-storey building. The height of the point from where the boll is
thrown is 25.0m from the ground (a) How high will the ball rise? and (b)
How long will it take to reach the ground?​

Answer 1

Lets take g = 10 m/s²

u = 20 m/s

v= 0m/s

v = u-gt

0= 20-10t

t = 2s

Distance from top of tower to top of position reached

S = ut - 1/2gt²

S = 40 -5*4

S = 20m

Distance from ground to top of building = 25-20 = 5 m

If the ball takes 4 seconds to cover 40m it will take 4.5 seconds to cover additional 5 m that is 45 m