Types of friction

We find it difficult to move the heavy sofa in our living room.

When we push it initially the sofa doesn't move. But if we continue applying force then the sofa moves after some time.

Initially, the sofa does not move because there is a opposing force present between the sofa and the surface on which it is lying.

This force is the force of friction.

But after we increase the force gradually, it overcomes the force of friction and thus the sofa starts to move.

When the sofa starts its motion, there exists another kind of force of friction which is different from the earlier one when the sofa was at rest.

Hence, there are some kinds of friction which we have to study.

Let's study the different types of friction.

Initially, the sofa doesn't move because of the static friction. The force we apply is balanced by the frictional force.

Static friction is considered a self-adjusting force because it wants the objects to remain at rest and not move.

After gradually increasing force, the sofa begins to move. In this case, the friction acting is sliding friction.

Let's discuss this with the help of a simple graph. consider the force we apply is a horizontal force represented on the axis.

And the frictional force applied is represented on the axis.

Now, as we increase the horizontal force applied, the frictional force is also increasing accordingly to keep the sofa at rest.

This continues till the point where the sofa just starts moving and that's where the static friction ends and the sliding friction begins.

If we have ever pushed a sofa or some heavy object on the floor, then we must have realized that the pushing becomes little easier when the object is in motion.

It's because the sliding friction is lesser than the static friction offered by the floor.

We can make it more easier by adding wheels to the sofa. So the sofa is not going to slide now rather It's going to roll.

When a body rolls over the surface, the resistance to its motion is called rolling friction.

That's why we observe the luggage bags have wheels attached to them because it is easier to roll than slide them.

Because of this reason we consider the invention of the wheels as one of the greatest invention of mankind.

Therefore the order of these frictions is,

Revision

The force required to overcome friction and at that instant an object starts moving from rest is static friction.

The force which we required to overcome to keep the moving object in the same speed is sliding friction.

When a body rolls over another body, the resistance to its motion is called rolling friction.

We can arrange the different frictions in the order shown as,

The end