Question

From a building two balls `A` and `B` are thrown such that `A` is thrown upwards and `B` downwards ( both vertically with the same speed ). If `v_(A) and v_(B)` are their respective velocities on reaching the ground , then
A. `v_(B) gt v_(A)`
B. `v_(A) = v_(B)`
C. `v_(A) = v_(B)`
D. their velocities depend on their masses.

Answer 1

Correct Answer - B
Let the ball A is thrown vertically upwards with speed u and ball B is thrown vertically downwards with the same speed u.
After reaching the highest point, A comes back to its point of projection with the same speed u in the downward direction, then velocity of A on reaching the grounds is
`v_(A)^(2)=u^(2)+2ghorv_(A)=sqrt(u^(2)+2gh)" ..."....(i)` and that of B on reaching the ground is
`v_(B)^(2)=u^(2)+2ghorv_(B)=sqrt(u^(2)+2gh)" ".........(ii)`
From eqns (i) and (ii), we get `v_(A)=v_(B)`