Final answer:
Friction is the force that stops the sled from moving. Materials with low friction, like ice or waxed plastic, allow the sled to slide longest, while materials with high friction, like sand or rough concrete, make the sled stop fastest.
Step-by-step explanation:
The sled stops moving due to the forces acting on it. Friction between the sled and the surface it is sliding on slows it down and eventually brings it to a stop. The materials that make up the surface of the hill and the sled can affect how long it slides or how quickly it stops.
The longest sliding distance will be achieved on a surface with low friction, such as ice or waxed plastic. These materials have smooth surfaces that reduce friction and allow the sled to slide for a longer distance.
The fastest stopping can be achieved on a surface with high friction, such as sand or rough concrete. These materials provide more resistance and generate more friction, causing the sled to come to a stop more quickly.