Gravity on the Moon is about 1/6th that on the Earth. A
pole-vaulter 2 metres tall can clear a 5 metres pole on the Earth.
How high a pole could he clear on the Moon?
A simplified account of special relativity and the twins paradox.
A ball whooshes down a slide and hits another ball which flies off
the slide horizontally as a projectile. How far does it go?