A body projected from the ground reaches a point X in its path after 3 seconds and from there it reaches the ground after further 6 seconds. The vertical distance of the point X from the ground is (acceleration due to gravity =10 ~ms ⁻² )

Step-by-step solution

Total time of flight (t)= 2 u g or, 9= 2 u g or, u= 9 g 2 or, u= 9 10 2 or, u=45 ~m / s Since, in covering the vertical distance, g becomes - (ve) aligned & using h=u t- 1 2 g t^2 & =45 (3)- 1 2 10 (3)^2=135-45=90 ~m aligned