Question

Ball A is thrown in upward from the top of a tower of height h. At the same time ball B starts to fall from that point. When A comes to the top of the tower, B reaches the ground. Find the time to reach maximum height for A. 

(A) √(h/g) 

(B) √(2h / g) 

(C) √(h / 2g) 

(D) √(4h / g)

Answer 1

Correct option: (C) √(h / 2g)

Explanation:

For boll B

d = v₀t + (1/2) at² 

i.e.      h = (0) (t_B) + (1/2) gt_B² where t_B is time for B to reach ground

t_B = √(2h / g)

when ball B reaches ground, A will reach to top i.e. t_B = 2t_A where t_A is max height for A

∴ t_A­ = (t_B / 2) = (1/2) √(2h / g) = √(h / 2g)