1. You drop a ball from a window located on an upper floor of a building. It strikes the ground with speed v. You now repeat the drop, but your friend down on the ground throws another ball upward at the same speed v, releasing her ball at the same moment that you drop yours from the window. At some location, the balls pass each other. Is this location (a) at the halfway point between window and ground, (b) above this point, or (c) below this point? Someone said the solution is b. Subjectively this may be find and dandy, but does any have proof of this using equations? I tried to find the time of each ball to reach halfway and then compare. Using the dropped ball as t1, i get t1 = SQRT(h/g), where h is the height of the building. Using t2 as the thrown ball, i have to solve t2 as a quadratic formula (1/2 h = vt-1/2gt2), in which case i have t2 in terms of v, g, and h. however I had no way to compare the two time intervals.