Question

15. (a) How long will a stone take to fall to the ground
from the top of a building 80 m high and (b) what
will be the velocity of the stone on reaching the
ground ? (Take g = 10 m s2)​

Answer 1

GIVEN:- Distance=height of the tower=s=80m

Acceleration=g=10m/sec^2

Initial velocity=u=0m/s. (because the stone is falling from rest under free fall)

TO FIND:-a)time =t, b)final velocity=v

a)

To find t we have to use this formula that s=ut+1/2gt^2

80=0*t+1/2*10*(t)^2

80=0+1/2*10t^2

80=0+5t^2

5t^2=80

t^2=80/5

t^2=16

t=√16

t=4sec

b)

To find v we have to use this formula g=(v-u)/t

10=(v-0)/4

10*4=v

v=40m/sec

HOPE THIS WILL HELP YOU