Friction is of three types
- Static Friction
- Sliding Friction
- Rolling Friction
Let's study each of them
Static Friction
Static friction is the frictional force which keeps the object at rest.
Example
A rock is lying on mountain slope
It is not moving down inspite of the slope
This is because of static friction between the rock and the slope
We have to move the rock by pushing it(applying a force),only then it will fall from mountain
Sliding Friction
Sliding friction is the frictional force on the object when the object is moving (or sliding) over a surface
It is also called Kinetic Friction
Example
child sliding down through a slide in a park
Skis sliding in snow
Which is Smaller- Static or Sliding Friction?
Sliding friction is always smaller than Static friction
This is because it is easier to keep a moving object moving (Sliding friction)
But it is more difficult to make a stationary object to move(Static friction)
Example
It is easier to push a moving car but more difficult to push a car which is standing
Reason
When the object is in motion, the irregularities of the moving object doesn't get much time to interlock with the irregularities of the surface.
Since the interlocking is less, the frictional force will be smaller
Hence, Sliding Friction is smaller than Static Friction
Rolling Friction
Rolling friction is the frictional force on the object when the object rolls over a surface
Example
If we move a heavy bag, it is very hard to move
But if we move a heavy bag containing wheels, it is much easier
This is due to less friction because of rolling of wheels
Since it is easier to roll than to slide
So, Rolling friction is less than sliding friction
Difference between Static, Sliding and Rolling Friction
Static Friction | Sliding Friction | Rolling Friction |
Static friction is the frictional force which keeps the object at rest. | Sliding friction is the frictional force on the object when the object is moving (or sliding) over a surface |
Rolling friction is the frictional force on the object when the object rolls over a surface
|
It is highest | It is lower than static friction, but higher than rolling friction | It is the lowest |