Hi, Im haveinga problem setting up an equation. 1) A ball is thrown upward with initial velocity of 80 m/s. a) how long is the ball in the air? b) what is the greatest height reached by the ball? c) when is the ball 20 m above the ground? d)what is the velocity of the ball, when it hits the ground? Im having problem setting up the equation in part d. Thank You.