posted by Sam .
You and two friends are on top of the library 30 m above the ground. At the same time that you drop a ball, from rest, one of your friends tosses a ball straight up, giving it an initial velocity of 15 m/s, and your other friend tosses a ball straight down, giving it an initial velocity of -15m/s. Note that each ball, once released from the tosser's hand will accelerate at -9.8m/s^2.
a) Assume the t=0 sec corresponds to when the three balls were released, what times will each ball strike the ground?
b) When the ball was tossed downward is 15 m above the ground, what will be the positions of the other two balls?