Question

What is the effect of friction on mass?

Answer 1

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 prop 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=muN=muF` 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=mg`

Or, `muF=mg`

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 `fpropF`

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.