February 2019
Intermediate to advanced
292 pages
6h 55m
English
Imagine bouncing a ball to your dog. You toss the ball to the ground at a point halfway between the two of you, the ball bounces up, and your dog (if she is well trained) catches it, like the following figure illustrates.

The ball’s velocity is reflected around the normal at the point where it hits the ground. That is to say, it keeps moving forward, but instead of falling as it does so, now it is rising. Anyone that has ever played with a ball will know intuitively what that means. We all know from experience which direction the ball is likely to bounce.
Write the following two tests to reinforce that intuition. You’ll introduce ...
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