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Lunar Leaper

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?

Which Twin Is Older?

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?

Earth Orbit

Age 16 to 18
Challenge Level

For the first part you will need to change variables in an equation. You will need to use this idea:$$\frac{df}{dr} = \frac{df}{du}\frac{du}{dr}\;.$$ For the second part, you need to redefine your angle by shifting it by a certain amount.