Final answer:
A skateboarder will experience more friction skating on grass due to higher resistance and less friction on ice because of a lubricating layer of water. Kinetic friction is the relevant type of friction when in motion, and it's lower on ice compared to grass.
Step-by-step explanation:
The friction experienced by a skateboarder will vary significantly based on the surface they're riding on. When skating on grass, the friction is higher because the irregular and soft nature of grass creates more resistance against the skateboard's wheels. On the other hand, when skating on ice, friction is lower due to the presence of a thin layer of water on the ice, which acts as a lubricant, reducing the resistance to movement.
Static friction is usually higher than kinetic friction, but in the context of skating, the relevant friction is kinetic since it involves movement. Grass provides more resistance and therefore more kinetic friction, which slows down the skateboarder more quickly than ice. On ice, the reduced kinetic friction allows for smoother and longer glides.