From the top of a tower, a ball is thrown vertically upward which reaches the ground in 6   s . A second ball thrown vertically downward from the same position with the same speed reaches the ground in 1 . 5   s . A third ball released, from the rest from the same location, will reach the ground in _____ s.

Step-by-step solution

When it is thrown upward, - h = v × 6 - 1 2 g 6 2 When it is thrown downward, - h = - v × 1 . 5 - 1 2 g 1 . 5 2 Therefore, 5 h = 5 36 + 9 h = 45   m When the ball is dropped, h = 1 2 g t 2 ⇒ 45 = 1 2 × 10 × t 2 ⇒ t = 3   s Alternate method, t = t 1 t 2 = 6 × 1 . 5 = 3   s