we know if we apply the force along the left, friction acts along the right and vice versa. But what about an object which is not moving but at rest on a surface?

Explanation below

Explanation:

Friction Force

When two objects are in contact, the surface between them exerts a frictional force as long as the objects are tried to move with respect to each other.

If a given external force is applied to the left, then a friction force appears to the right and opposes the intent to move them. A similar situation occurs when the force is applied to the right side.

If the object is at rest and no force is applied, no friction force appears.

It's important to recall that two different friction forces are defined: the kinetic friction force and the static friction force, usually the latter is greater than the first.

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