Question

A stone thrown vertically upwards with initial velocity reaches a height 'h' before coming down.show that the time taken to go up is same as the time taken to come down.

Answer 1

We have v=u+at

and s=ut+12at2

∴s=(v−at)t+12at2=vt−at2+12at2

s=ut−12at2

As the stone moves upward from A→B

S = AB = h, t = t1, a= - g ( retardation )

u = u and v = 0

h = 0−12(−g)t21

h=12gt21

As the stone moves downward from B→A

t=t2,u=0,s=h and . h=12gt22

From Eqs. (4) and (5) , t21=t22

t1=t2