A ball rolls forward in the grass slowing down as it rolls?

Yes it does, uh huh. It slows down as it rolls. That's a fact.

In order for the ball to roll forward, it has to push grass out of the way. That takes energy. To bend each blade of grass out of its way, the ball has to use a tiny bit of the kinetic energy that it has, so it gradually runs out of kinetic energy. When its kinetic energy is all gone, it stops moving.