Question

Why sliding friction is less than static friction?

Answer 1

Sliding friction is less than static friction, because, static friction is the type of friction that exists when two objects touch each other at rest. Sliding friction is a type of friction that exists when an object slides over the other relatively. The force needed to overcome the friction at that instant an object starts moving rest is a measure of static friction. On the other hand, the force required to keep the object moving with the same speed is a measure of sliding friction.

OR
The friction is due to the interlocking of irregularities in the two surfaces. When the object starts sliding the contact points on its surface, do not get enough time to lock into the contact points on the floor.