Two balls of equal masses are thrown upwards, along the same vertical direction at an interval of 2 seconds, with the same initial velocity of `40m//s`. Then these collide at a height of (Take `g=10m//s^(2)`).

Options

A. 50 m
B. 75 m
C. 100 m
D. 125 m

Answer

B

Explanation

`s_1=s_2`
`:. (40)t-1/2xx10xxt^2=(40)(t-2)`
`-1/2xx10xx(t-2)^2`
Solving this equation, we get
`t=5s`
Then `s_1=(40)(5)-1/2xx10xx(5)^2`
`=75m`