### 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.

### Whoosh

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.