The correct answer is: C. Both (A) and (B).
The coefficient of friction is a measure of how much two surfaces resist each other when they are sliding against each other. It is a dimensionless number that is always less than or equal to 1. The coefficient of friction depends on the nature of the surfaces in contact, as well as the area of contact.
The nature of the surfaces in contact refers to the roughness and smoothness of the surfaces. Rough surfaces have more friction than smooth surfaces. This is because the rough surfaces have more points of contact, which creates more resistance to movement.
The area of contact refers to the amount of surface area that is in contact with each other. The larger the area of contact, the greater the friction. This is because the larger the area of contact, the more points of contact there are, which creates more resistance to movement.
The coefficient of friction is an important factor in many engineering applications. For example, it is used to design brakes and clutches. It is also used to design tires and other parts that need to grip surfaces.
Here are some additional details about each option:
- Option A: Nature of surfaces only. This is incorrect because the coefficient of friction also depends on the area of contact.
- Option B: Area of contact only. This is incorrect because the coefficient of friction also depends on the nature of the surfaces in contact.
- Option D: None of the above. This is incorrect because the coefficient of friction does depend on both the nature of the surfaces in contact and the area of contact.