Do you understand Newton’s Laws?
Many do not know Newton’s Laws of motion but think they do
Perhaps you do understand Newton’s laws but then you’d be a part of a small fraction of people who think they understand Newton’s laws of motion and actually do. Odds are, you should read on.
1st Law: An object at rest stays at rest and an object moving keeps moving with with same speed and in the same direction
2nd Law: Net force on an object is equal to mass times acceleration
Do you agree with the above? Then you do not understand Newton’s laws of motion.
What happens if I put net force to zero in the second law. I get the first law. So why have the first law as a separate law?
The reason is that the 1st law is not how its stated above. It actually says “In an inertial frame an object at rest stays at rest and an object moving keeps moving with with same speed and in the same direction”. These 4 little words make a world of difference.
In Newton’s days, space and time were obvious (this was before Einstein when they became when space and time got mixed up (literally)) and force was also pretty obvious in that one had horses and spring balances. So what was Newton trying to say in the first law? He was defining the frame in which one can use the 2nd and the 3rd law. So, he said that if you want to analyze the dynamics of a body, first go to an inertial frame by checking that objects with no forces acting on them are either at rest or moving with constant velocity.
Now let’s get to the second law. Since force has already been used in the first law clearly it’s not being defined in the second. Also acceleration is a pretty obvious thing if position and velocity are. So the thing being defined here is mass. The effect of the net force on a body is inversely proportional to a property of that body which is called mass.
The third law is also not understood properly by several people and I will write a short note about it some other day.
