1.

A stone is thrown upwards from the top of a tower with some initial speed and it reaches the ground in second. Now it is allowed to fall with the same initial speed downward and it reaches the ground in 1 second In how much time will it reach the ground if the stone is allowed to fall freely under gravity from the same place:

Answer»

`((t_1+t_2)/(2))`
`((t_1-t_2)/(2))`
`sqrt(t_1 t_2)`
`(t_1 +t_2)`

Solution :The equationof motion in three CASES are :
`h=-ut_(1)+(1)/(2)g t_(1)^(2)`
`h=ut_(2)+(1)/(2)g t_(2)^(2)`
`h=0+(1)/(2)g t^(2)`
USING `(1)/(2) g t^(2) =(1)/(2)g t_(1) t_(2) IMPLIES t=sqrt(t_1 t_2)`


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