Question

Riley is doing an experiment working with friction. He wants to find two ways to modify an object that could increase or decrease the same type of friction

Answer 1

If the type of friction is sliding friction, it may be increased by increasing the roughness of the surface and may be decreased by smoothing the surface or applying a lubricant.

Answer 2

Answer:

As we know that friction force is a contact force which opposes the relative motion between two surfaces in contact.

So here we can change the force between two surface when they move relative to each other.

Here when Lubrication is used between two surface then the relative motion of two planes becomes easy. So by lubrication of the surface either by oil or by smoothing the plane we can say that friction force will be reduced.

Also friction force depends on the effective contact points between two surfaces. So as we increase the contact points between two surfaces then the effective frictional force will increase.

Also we know that friction force is given by

$F_f = \mu F_n$

now as we increase the normal force between two contact planes either by increasing the weight or by applying normal external force we can say that friction force will increase.