You (yellow), need to pass the red ball to your friend (blue), as you both sit on a merry-go-round. I posted a similar animation of this problem before- and this one shows quite an extreme of the solution. You can only throw the ball very slowly, so you throw the ball to where your friend will be when it gets to them. From above, the ball travels in a straight line, but in the world of the spinning merry-go-round that you occupy- the ball seems to be warped on a curve by some invisible forces. These invisible forces are called the Coriolis and Centrifugal effects. [code] [more]