Book 28, Question 17
Why does a ball slow down faster on grass than on a gym floor?
A rolling ball pushes into the surface and bends or squashes it a little.
Soft grass bends and tangles, which takes more energy than rolling on a hard, smooth floor. The ball also bumps along the tips of blades. The ball keeps losing speed to these small forces. This is called rolling resistance. Wet or long grass slows the ball even more.