русский
коэффициент трения португальский
fricção испанский
fuerza de fricción каталонский
forces de fricció 
Force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.
испанский
fuerza de fricción dinámica Force opposing the motion of a body sliding on a surface.
1
It is the friction force and it is parallel to the surface.
2
Anyway, perhaps you see an important aspect of the friction force.
3
Fortunately, we have a pretty good approximation for the friction force.
4
When two surfaces rub against each other, why is there a friction force?
5
This model says that the surface area doesn't have an impact on the friction force.
6
The friction force also depends on the normal force.
7
Since the friction force and the displacement are in the same direction, the work is positive.
8
In this case, the friction force (on both his hands and feet) push up.
9
The only difference would be that the friction force would be replaced by some other force.
10
So for our energy perspective on this problem let's just say the human provides the friction force.
11
That's because you need the largest friction force because the pole pushes only in the horizontal direction.
12
The friction force is essentially from me (the rider).
13
Here is a fairly normal model for sliding friction : This is just the magnitude of the friction force.
14
The story force wants to go forward and the " friction force" of challenge tries to hold story back.
15
This means that the magnitude of the friction force will be: With this, I can eliminate the friction force from the two equations.
16
The usual model for the static friction force (for a non-sliding tire) says that this friction force is proportional to the normal force.