Answer:
The relationship is the normal force, that is equal to the product of the mass by gravity.
Step-by-step explanation:
The friction force is defined as the product of normal force by the value of the coefficient of friction, in this way we have:
f = μ * N
Where:
f = friction force [N]
μ = friction coefficient
N = normal force [N]
On a flat surface, the normal force is equal to the weight of the body, this way we have:
N = m*g
Therefore:
f = μ * m * g
We can conclude that for a flat surface the friction force depends on the coefficient of friction, this is a value that depends on the surfaces in contact, and the weight of the body.