When you know about Physics, in generally you will find the Newton’s law – the 1st , 2nd and 3rd. These law had a fundamental role in our classical physics.
The Newton’s Law is Empiric law from experience of life. It may be stated in a brief form as below:
1. In inertial systems, The state of an object motion not change as period during there is no external influences. Every object continues in its state of rest or moving uniform in a straight line.
2. The External Force will change a momentum of an object.
3. A momentum of systems is conservative unless there is no an external forces.
Talking a Newton, we will start with Mass as an intrinsic property from an object.
Mass is an intrinsic quantity from an object which is showing response to the an external influences like a Force. The conceptual of Mass in physics not about an amount of substance or matter, but how big it resistance due to the external forces.
For Example, based on The 2nd of Newton ‘s Law F = dP/dt , this is a causality principle. The nature of law have to obey this principle. So the external forces will play as cause role and mass within response a Force will change a speed of object.
Furthermore, the 3rd of Newton’s Law known as a couple of action-reaction force. When you try more objective that this law yield a change of momentum from it derivatives. Momentum is motion quantity which is belongs to an object has change when force hit the object.
(Source: All thought from lecture in my class, to my Prof Husin Alatas, Theoretical Physics in IPB)
Physics is a knowledge that explain universe and natural phenomena. Since you try to objective with that, you will find a lot of interesting therein and Physics is Top of the line as science.