A ball is thrown vertically upwards with a speed of `10 ms^-1` from the top of a tower 200 m high and another is throwtl .vertically downwards with the same speed simultaneously. The time difference between them in reaching the ground, in second, if g is taken as `10 ms^-2`, is

Options

A. 12
B. 6
C. 2
D. 1

Explanation

`|barA+barB|=|barA+barB|`
Squaring on the both sides
`|barA+barB|^2=|barA-barB|^2`
`implies|A|^2+|barB|^2+2(|barA|.|barB|)=|barA|^2+|barB|^2-2(|barA|.|barB|)``implies4|barA|.|barB|=0`
`implies4ABcostheta=0`
`impliescostheta=0`
:.theta=90^0`