Question

Why frition doesn't roll a ball backward if no force is pushing or pulling it?

Answer 1

Friction is a force that opposes relative motion
it doesn't act on bodies at rest

Answer 2

A nice question!!
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So, you are asking that if friction opposes motion then why it doesn't rolls back a moving body?

The answer is in the definition of friction. Well frictional force is a force opposing motion of a particle, so this means that friction acts only on a moving body. If friction would role back an object then it would start contradicting it's basic definition.

Let's consider an example. Suppose a rectangular block is kept on a table, you decide to slide it, you apply a force on one of it's end, now according to Newton's First Law of Motion that rectangular block is expected to remain in the state of motion, but it comes to rest due to friction.

This shows that friction actually retards a body and puts it to rest. If we take a hypothetical situation where friction starts motion in the above mentioned block backward, then it would actually be producing motion rather than opposing it.

Hope it helps ^_^

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Regards,

TheBlaze