If frictional force F=µR. Then µ=F/R = ma/mg = a/g. So, coefficient of friction is proportional to acceleration. But if the acceleration of a body increases, then the coefficient of friction should decrease right?

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anonymous · Answer

You have written F=ma but F is not a net force, it is frictional force. And according to newton's second law "Net force = mass * acceleration in the direction of force."
So coefficient of friction is doesn't depend on acceleration. It depends the surface of contact.