Law of Inertia

Mechanical systems are subject to the law of inertia. The law
of inertia states that an object will tend to remain in its current
state of rest or motion unless acted upon by an external force.
This property of resistance to acceleration/deceleration is
referred to as the moment of inertia. The English system of
measurement is pound-feet squared (lb-ft2).
If we look at a continuous roll of paper, as it unwinds, we know
that when the roll is stopped, it would take a certain amount
of force to overcome the inertia of the roll to get it rolling. The
force required to overcome this inertia can come from a source
of energy such as a motor. Once rolling, the paper will continue
unwinding until another force acts on it to bring it to a stop.