There’s some nifty physics behind the dam-busting bombs that were used by the British in WWII. Just like skipping stones, to make a bomb bounce off water you need to have enough speed and a perfect angle (about 7° in the case of the bomb).
If you get these just right, conservation of momentum means that the water pushes back on the bomb and kicks it up in the air. For multiple bounces, the magic ingredient is spin. Spin the bomb and you stabilise its motion, like a frisbee or a gyroscope.
The designers of the bouncing bomb made use of these principles, with the aim of saving the British bombers the tricky task of hitting a German dam bang on target. The cylindrical bombs were spun on launch, making them bounce several times, and as the bombs completed their final bounce, the spin even made them sink in a curved trajectory towards the dam.
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