A stone dropped from a building of height h and it reaches the ground after t seconds. From the same building if two stones are thrown (one upwards and other downwards) with the same velocity u and they reach the ground after t1 and t2 seconds respectively, then
The correct option is B t=√t1t2
Step 1, Given data
Height of the building = h
Time taken to reach the ground = t
Two other balls are thrown in upward and downward directions simultaneously.
Step 2, Finding the relation
Taking downward as positive
For first case of dropping the stone, h=12gt2
For second case of downward throwing h=ut1+12gt21=12gt2
Or we can write
⟹ut1=12g(t2−t21)......(i)
For third case of throwing upwards h=−ut2+12gt22=12gt2
Or we can write
⟹ut2=12g(t22−t2)....(ii)
On solving (i) and (ii) we get,
t1t2=t2−t21t22−t2
Or,
⟹t=√t1t2
Hence the relation is as given above.