Question

What are two important properties of friction?

Answer 1

The term friction is associated with the frictional force. First we need to understand what factors the force of friction acting on a body depends upon which will enable us to establish a link between its properties. Further by analyzing the mathematical equation of frictional force we will be able to conclude the nature of frictional force.

Formula used:
${{v}_{o}}=\sqrt{\dfrac{g{{R}^{2}}}{R+h}}$
${{v}_{e}}=\sqrt{2gR}$
Formula used:
$f=\mu N$

Complete answer:
To understand friction consider a wooden block resting on a horizontal floor. If we push the block, after some time the block comes to rest. This is only possible if there is a force retarding the motion of the block. This opposing force is called friction. The force (f)due to friction is given by,
$f=\mu N$
Where $\mu$is the coefficient of friction and ‘N’ is the normal force by the floor on the block.
Coefficient of friction is related to the property of the surface i.e. it is a measure of how smooth the surface is. For a completely smooth surface $\mu =0$, implies friction is zero.
Hence from the above information we can conclude some of the properties of frictional force as
a) Always acts in the opposite direction to that of the motion of a body.
b) It depends on the normal reaction between the two surfaces held in contact as well as the nature of the surfaces.

Note: The force of friction is due to the atomic or molecular forces of attraction between the two surfaces at the points of actual contacts. It is also to be noted that the friction is a component of co0ntact force. Frictional force is a non conservative force as the energy spent against it is lost in the form of heat.