Red Ball, Blue Ball
In what direction do I shoot the red ball so it will collide with the blue?
At time t = 0 a red ball is projected from the origin and travels along the line y = mx at constant speed 2. At the same moment a blue ball is dropped from the point (4, 4) and travels down the line x = 4 at constant speed 1. What value of m will produce a direct collision of the two balls? Of course the fun part is constructing the animation and deciding what you want to happen when the two balls do collide.