A baseball is thrown vertically upward with an initial velocity of 20m/s. A, what maximum height will it attain? B, what time will elapse before it strike the ground?
C, what is the velocity just before it strike the ground?​

The man of mass m1 and the woman of mass m2 are standing on opposite ends of the platform of mass m0 which moves with negligible friction and is initially at rest with s = 0. the man and woman begin to approach each other. derive an expression for the displacement s of the platform when the two meet in terms of the displacement x1 of the man relative to the platform.