# What is the effect of friction on mass?

Mar 15, 2018

Friction can't affect mass of a substance(considering for a substance whose mass doesn't change with time),rather it is the mass of an object which can affect friction variously.

Let's take some example to understand the situation.

Suppose a block of mass $m$ is lying on a table,if the coefficient of frictional force between them is $\mu$ then maximum amount of frictional force ($f$) that can act at their interface is mu×N=mumg (where,$N$ is the normal reaction provided by the table on the block,and it is equals to its weight)

So,for $\mu$ is a constant,

$f \propto m$

So,higher the mass of the object,higher will be the frictional force.

Now,suppose,you are pushing a block of mass $m$ against a vertical wall applying a force of $F$ on it,which keeps it at rest.

So,here frictional force acting is $f = \mu N = \mu F$ as here normal reaction provided by the wall equals the force applied on it.

Which tends to balance the weight of the block,

So, $f = m g$

Or, $\mu F = m g$

But,here you can see that mass of the block has no effect on the frictional force rather it depends on how harder you apply the force $F$ as $f \propto F$

So,only in case when normal reaction is directly proportional to the weight,only in that case mass plays an important role in the determination of frictional force that can act.