Question

why is sliding friction less than static friction? and why is rolling friction less than sliding friction?

Answer 1

The term sliding friction refers to the resistance created by two objectssliding against each other. This can also be called kinetic friction. Sliding friction is intended to stop an object from moving.
Rolling resistance, sometimes calledrolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface.
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Answer 2

When an object starts sliding the contact points on its surface do not get enough time to lock into the contact points on the floor so, the sliding friction is less than static friction . The rolling friction that exist between two surfaces when a body rolls over the other body but the sliding friction acting between two bodies when they slide on one another with a uniform speed so, the rolling friction is less than the sliding friction