Why doesn't a ball roll on forever after being kicked at a soccer game

The ball has to push things out of its way in order to keep going.

For example:

- - billions of air molecules

- - hundreds of blades of grass.

- - To push something out of its way, the ball exerts a force against the

obstacle, and pushes it some distance.

- - A force acting through a distance is 'work', and that means 'energy'.

- - The ball has a certain amount of energy ... the amount you gave it

when you kicked it. It gives every air molecule and blade of grass a

little bit of energy, so the ball has less and less as it goes along.

- - Eventually, it has no more energy to use to push things out of the way.

No energy means no motion, so it stops.

- - If it were in space where there are no air molecules and no grass,

it would go on forever.