In my one of earlier articles on Newton’s law, I have discussed about the Newton’s second law. We all are also aware about the Newton’s first law which mainly states that if an object is at rest will remain at rest and if it is in uniform motion will remain in uniform motion until and unless some external force is applied on it.
But do you know that the Newton’s second law is known as the real law of the motion. Let us prove it by showing that the Newton’s first law is contained in the second law.
Proof: let us take an isolated system that is system isolated or free from external forces.
From this law F = ma, where F is force, m is mass of object and a = acceleration.
As the system is isolated, thus F =0, therefore above equation becomes:
ma = 0,
but m can not be zero, thus a= 0 that is acceleration is zero of the object.
It is only possible when the object is at rest or in uniform motion and this is nothing but Newton’s first law.
It proves that the Newton’s first law is contained in the second law and thus proves that the Newton’s second law is the real law of motion.