A stone is allowed to fall from a top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. The two stones will melt after :

Options

A. 40s
B. 0.4s
C. 4s
D. 0.04s

Answer

C

Explanation

`x = (1)/(2) g t^(2) " " . . . (1) `
` s = ut - (1)/(2) g t^(2)`
`100 - x = 25 t - (1)/(2) g t^(2) " ". . . (2)`
Adding (1) and(2) we get ,
100 = 25 t
`:. t = (100)/(25) = 4s`