Question

Soles of the shoes have grooves to __________ friction while oil is applied to door hinges to _______ friction.

• A. Increase
• B. decrease

Answer 1

1. The frictional force: It is a contact force that acts between the two surfaces in contact.
2. As we know on the microscopic level, even a smooth-looking surface has many small irregularities.
3. When an object moves over another object, these irregularities get interlocked and oppose the motion of the object.
4. In order to avoid slipping soles of the shoes have grooves which increase irregularities on the surface as a result, friction is increased.
5. Oil or lubricant forms a thin layer between the two rubbing surfaces which results in smoothing of the irregularities therefore frictional force is reduced.

Hence, soles of the shoes have grooves to increase friction while oil is applied to door hinges to reduce friction.