Question

A stone dropped from the top of a tower reach the earth at 4 sec find height of the tower

Answer 1

hey mate

h=u²/2g

and

t=2u/g

u=t*g/2

=4*9.8/2

=4*4.9

=19.6 m/s

thus,

h=u²/2g

=19.6*19.6/2*9.8

=19.6 m (answer)

Answer 2

Given,

t=4s

acceleration=9.8m/s2

u(initial velocity)=0m/s

We know,

S=u*t+(1/2)*a*t*t

=0*4+(1/2)*9.8*4*4

=0+9.8*4*2

=78.4

Height of tower is 78.4 m