Final answer:
Friction is necessary on a bike to stay balanced and stable, when skis or skates slide over ice or snow the friction creates a layer of melting ice or snow which reduces friction, and the more electrons repel each other, the higher the friction.
Step-by-step explanation:
Friction is a force that opposes relative motion between surfaces in contact. In the context of riding a bike, friction is necessary to stay balanced and stable while moving forward. Without friction, the bike tires would not grip the ground, making it difficult to stay upright.
When skis or skates slide over ice or snow, the friction creates a layer of melting ice or snow which reduces friction. This thin layer acts as a lubricant, allowing the skis or skates to slide more easily.
The more electrons repel each other, the higher the friction. This is because friction is caused by the attraction between molecules making up the two objects in contact. When there are more electrons, their repulsion increases the attractive forces between the molecules, resulting in higher friction.