Question

the relative velocity of the ball with respect to the elevator when the ball hits the elevator.

Answer 1

For ball : $u=18$ $m/s$ $a=-g=-9.8$ $m/s^2$

Velocity of elevator $v=2$ $m/s$

Time taken by the ball to strike the elevator $t=3.65$ s (solved earlier)

For ball : $V_y=u-gt$

$\therefore$ $V_y=18-9.8\times 3.65=-17.77m/s$

Relative velocity of ball w.r.t elevator $V_{be}=V_y-v=-17.77-2=-19.77$ $m/s$

$\therefore$ $V_{be}=19.77$ $m/s$ (downwards)