Friction / types of friction / friction angle

● Friction ::
A force acting parallel to the contact plane of any two objects in contact is opposed to their relative motion. This force is called friction force.

We can explain easily by an example -

Let consider a wood box moving in a plane

We apply a pushing force on wood box then it will move in forward direction of pushing force but a another force will opposes it's motion , and it's force is known a friction force , the friction force always work in opposite direction of pushing force .

● Types of friction ::
In general friction are two types

- static friction
- Dynamic friction

1. Static friction ::
The force of friction between two plan with no relative motion between them is called static friction force. Static friction force is self-managed in nature. It maintains resting state between two forces along with other forces acting on the object.
The value of static friction force always between 0 to 𝝁N

0 ⩽ F ⩽ 𝝁N

Where F = static friction force
𝝁 = static friction coefficient
N = perpendicular force

◆ Rememberable point -
There is no energy loss due to static friction, that is, we can do action against static friction

2. Dynamic Friction ::
The force of friction between two planes of relative motion is called dynamic friction. The magnitude of dynamic friction is proportional to the force acting between the two forces.

F ∝ N

F = 𝝁N

Where 𝝁 = Dynamic friction coefficient
N = Perpendicular reaction force
F = dynamic friction

◆ Rememberable point -
Dynamic friction always acts in the opposite direction to the motion of the object. The work done against it is conservative , so the heat changes, so there is always an energy loss in the condition of dynamic friction.

● Limiting friction ::
If the force exerted on the object is continuously increased, a condition occurs when the object is in a state of motion, in which case the maximum static friction force acts on the object, which is called the marginal friction force.

F = 𝝁R

Where R = perpendicular reaction force
𝝁 = static friction coefficient

◆ Rememberable point The magnitude of the marginal friction force depends on the nature of the contact forces and their roughness or smoothness, it does not depend on the area of the contact forces.

● Friction Angle ::
In the condition of limiting friction force the angle between perpendicular reaction force ( R ) and limiting friction force ( F ) is known as friction angle .

If the friction angle is 𝛂

Then tan𝛂 = F/R

F/ R = 𝜇 ( Friction coefficient )