Answer:
The coefficient of kinetic friction and the coefficient of static friction are both affected by the area of contact between two surfaces in contact. The following is a detailed explanation of how the values of these coefficients are affected by the area of contact.
The coefficient of kinetic friction is defined as the ratio of the force required to maintain a constant velocity between two surfaces in contact to the normal force pressing them together. It is a measure of the resistance to motion between two surfaces in contact. The coefficient of kinetic friction is affected by several factors, including the nature of the surfaces in contact, their roughness, and their temperature. However, the area of contact between two surfaces also plays a crucial role in determining the coefficient of kinetic friction.
The larger the area of contact between two surfaces, the greater the frictional force acting between them. This is because a larger area of contact means that there are more points of interaction between the two surfaces, which leads to a greater number of intermolecular forces acting between them. As a result, it becomes more difficult to maintain a constant velocity between two surfaces with a larger area of contact, and hence, the coefficient of kinetic friction increases.
On the other hand, the coefficient of static friction is defined as the ratio of the maximum force required to initiate motion between two surfaces in contact to the normal force pressing them together. It is a measure of the resistance to motion when an object is at rest on a surface. Like the coefficient of kinetic friction, it is also affected by several factors including surface roughness and temperature. However, unlike the coefficient of kinetic friction, it is not affected significantly by changes in area of contact.
This is because when an object is at rest on a surface, it does not matter how much area it covers on that surface. The maximum force required to initiate motion remains constant regardless of whether an object has a small or large area in contact with another surface. Therefore, changes in area of contact do not significantly affect the coefficient of static friction.