What runs but never walks, has a mouth but never talks, haves a head but never weeps, haves a bed but never sleeps?

river that joke is little old but still a good one

A river???

Explanation:

a river runs but it never walks. it has a mouth but never talks...a river has a head but never weeps, it has a bed but the river never sleeps... that rhymes don't ya think.

less than one you can't create energy