JEE Main202127 Jul 2021Morning ShiftPhysicsMotion in One DimensionActual
A ball is thrown up with a certain velocity so that it reaches a height h . Find the ratio of the two different times of the ball reaching h 3 in both the directions.
Options
- A2 - 1 2 + 1
- B1 3
- C3 - 2 3 + 2
- D3 - 1 3 + 1
Correct answer
C. 3 - 2 3 + 2
Step-by-step solution
u = 2 g h Now, S = h 3 ,   a = - g S = u t + 1 2 a t 2 h 3 = 2 g h t + 1 2 - g t 2 t 2 g 2 - 2 g h t + h 3 = 0 From quadratic equation t 1 ,   t 2 = 2 g h ± 2 g h - 4   g 2 h 3   g t 1 t 2 = 2 g h - 4 g h 3 2 g h + 4 g h 3 = 3 - 2 3 + 2