A ball is thrown vertically upward from the 12 m level with an initial velocity of 18 m/s. At the same instant an open platform elevator passes the 5 m level, moving upward with a constant velocity of 2 m/s. Determine ( g=9.8 m/s2 )
a. when and where the ball will meet the elevator,
b. the relative velocity of the ball with respect to the elevator when the ball hits the elevator.