Every object maintains a constant velocity unless acted upon by an unbalanced force. Newton claimed that the larger the mass of the object, the greater the force needed to change its velocity. Inertia is simply an object's resistance to change velocity. An object keeps traveling at one speed and continues to do so until an outside force acts on it. Examples of this can include a car accident.
Newton claims that objects have inertia no matter where they are.
The second law talks about the relationship between acceleration force, and mass. This mathematical equation states that the force put on the object, along with the objects mass determine the rate of acceleration. Newton's ability to rely on math to prove his theories set him apart from all others who previously came before him. The fact that he believed so strongly in math's role in science was very Cartesian, but that is perhaps the only the most important difference between the two. 3. The third law of motion states that for every force there must be an equal and opposite force.