Isaac Newton’s laws of motion are often taken as a given, without any explanation as to how they were arrived at. Hence my question, “Why are Newton’s laws?” Focusing on Newton’s second law, Force equals Mass times Acceleration (F = ma), I detect an influence from Galileo. Galileo dropped objects of different mass from the Tower of Pisa, in Italy. The Force was gravity; the Mass was the dropped objects; the Acceleration was their increasing speed as they rushed towards the ground. Yet plugging in Galileo’s experiment into Newton’s second law, F = ma, yields the Mass of the different objects to have been the same! There is an unsolved puzzle here.
Such reads the description of my latest video, “Why Are Newton’s Laws?”, published to YouTube on January 20, 2016. The clip, which clocks in at 8 minutes and 32 seconds, can hopefully be seen at the top of today’s blog entry.
In physics, one of the concepts encountered is, Action at a Distance. The venerable Wikipedia tells us that action at a distance is the concept that an object can be moved, changed, or otherwise affected without being physically touched (as in mechanical contact) by another object. 
The venerable Wikipedia tells us that the term, Action at a Distance, was used most often in the context of early theories of gravity and electromagnetism to describe how an object responds to the influence of distant objects.  The early theories of gravity would have to include those of Isaac Newton.
Prominent among Newton’s laws is his second law of motion: Force = Mass times Acceleration (F = ma). But WHY does the Force equal the Mass multiplied by the Acceleration?
What I have figured out is that it begins with Galileo. He was dropping objects off the Tower of Pisa, in Italy. The objects dropped from the tower are the Mass. And some Force causes the objects to rush towards the ground. And there is an acceleration of the objects – the mass – as they rush towards the ground. So there you have it: the Force (gravity), the Mass (the dropped objects), and the Acceleration (the speed they keep gaining until they hit the ground).
But here is a puzzle. Galileo dropped two objects of different mass from the tower. He dropped the two objects of different mass simultaneously. And both objects hit the ground at the same time. So we plug in Newton’s second law: Force = Mass times Acceleration. We know the Force; it is gravity. We know that the Acceleration was the same for both objects of different mass. Plugging in the Newton formula we have both Force and Acceleration being the same for both objects. So this would mean according to the formula that they both have the same Mass – BUT THEY DON’T.
So that is a little puzzle for you: Newton’s second law says both objects dropped from the tower have the same mass when in fact they don’t.
——- Sources ——-
 “Action at a distance”, Wikipedia, January 19, 2016.