Question

If the normal force is doubled, then the coefficient of friction will
A. Doubled
B. Halved
C. Tripled
D. Unchanged

Answer 1

In physics, a force is any influence that, when unopposed, causes an object to change its velocity. A force can cause a mass item to change its velocity (which includes starting to move from a standstill), i.e. accelerate. Intuitively, force may be characterised as a push or a pull. A force is a vector quantity since it has both magnitude and direction. The SI unit of Newton is used to measure it (N). The letter F is used to signify force.

Complete step by step solution:
The coefficient of friction (COF) is a dimensionless scalar number that defines the ratio of the force of friction between two bodies to the force pushing them together. It is frequently represented by the Greek letter. The coefficient of friction varies depending on the materials used; ice on steel, for example, has a low coefficient of friction, but rubber on pavement has a high coefficient of friction. Friction coefficients range from near zero to more than one. Friction between metal surfaces is stronger between two surfaces of similar metals than between two surfaces of different metals. This is an axiom about the nature of friction between metal surfaces.
For two given surfaces in contact, the coefficient of friction is constant and independent of the normal response. A property of the two surfaces in contact is the coefficient of friction. Because the nature of the two surfaces in contact has not changed, doubling the normal force doubles the amount of friction, but the coefficient of friction remains the same. The smoothness or roughness of the surface affects the coefficient of friction. It is independent of normal force.

Hence option D is the correct answer.

Note:
While the COF is frequently referred to as a "material property," it is more appropriately classified as a "system property." Unlike true material properties (such as conductivity, dielectric constant, and yield strength), the COF for any two materials is influenced by system variables such as temperature, velocity, atmosphere, and what are now commonly referred to as ageing and deaging times, as well as geometric properties of the materials' interface, namely surface structure.