In Physics, force is defined as: The push or pull on an object with mass that causes it to change its velocity. Force is an external agent capable of changing the state of rest or motion of a particular body. It has a magnitude and a directionForce is an external agent capable of changing the state of rest or motion of a particular body. It has a magnitude and a direction. The direction towards which the force is applied is known as the direction of the force and the application of force is the point where force is applied.
The Force can be measured using a spring balance. The SI unit of force is Newton(N).
We divide the thin rectangular sheet in small parts of height b and length dr. All these sheets are parallel to b. The infinitesimal moment of inertia of one of these small parts is where Now we find the moment of inertia by integrating from to The moment of inertia is (from (-a/2) to (a/2))
to 
(from (-a/2) to
(a/2))