1) Friction is desirable in braking of a vehicle. As brakes are applied, friction between brake shoes and tyres opposes rotation of tyres and hence, forces it to stop.
2) Friction between moving parts in machines is undesirable, because the moving parts rub against each other, heat up, and wear out. Friction can be reduced by lubricating the surfaces.
Answers & Comments
Answer:
1) Friction is desirable in braking of a vehicle. As brakes are applied, friction between brake shoes and tyres opposes rotation of tyres and hence, forces it to stop.
2) Friction between moving parts in machines is undesirable, because the moving parts rub against each other, heat up, and wear out. Friction can be reduced by lubricating the surfaces.