Newton’s second law describes what happens when a force does act upon an object. This is described quantitatively. The second law also pertains to the behavior of objects when all existing outside forces aren’t balanced. The acceleration of an object is dependant upon two variables. The two variables are the net force and the mass of the object.

The net force is the vector sum of all forces acting on an object. An object’s mass is the amount of inertia and matter in an object. When object is accelerating its acceleration depends upon the net force acting on it, and inversely upon the mass of the object. If the object’s mass increases, its acceleration will decrease. Remember that an object’s acceleration is directly proportional to the net force.

This is an image from nasa.