Answer:
Coefficient of friction = Magnitude depends on the interacting materials
Friction = A force that acts parallel to the surface.
kinetic friction = A force that is constant regardless of the applied force
Normal = A force that acts perpendicular to the surface
Static friction = A force that increases as applied force increases up to some maximum value
Explanation:
Let's define all the forces, and then let's solve the problem.
Normal force:
When an object rests on some place (like a book on the table) the force that causes the book to not fall through the table is called the normal force, which is usually equal to the weight of the object and acts perpendicular to the surface where the object is resting.
Friction force.
When an object moves (or tries to move) parallel to a surface, such that the object is in contact with that surface, there appears a force that opposes to the movement (the force is parallel to the surface, and in the opposite direction to the movement).
And this force can be written as:
F = -N*μ
Where μ is the coefficient of friction and N is the normal force.
If the object is not moving yet (but there is applied a force that would move the object) the coefficient is called the coefficient of static friction which increases in a given range, until it can't keep increasing and the object starts to move, while if the object is moving, the coefficient is called the coefficient of kinetic friction and it is constant, where usually the first one is larger than the second, and these coefficients depend on both materials, the surface one and the object one.
Then we have two friction forces, one called the kinetic friction and the other called the static friction.
Then:
Coefficient of friction = Magnitude depends on the interacting materials
Friction = A force that acts parallel to the surface.
kinetic friction = A force that is constant regardless of the applied force
Normal = A force that acts perpendicular to the surface
Static friction = A force that increases as applied force increases up to some maximum value
, so its density is: