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Laws of Motion

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I’ve been meaning to write on this subject for a while, but never quite found the right forum. I did a few searches on the internet, but didn’t find anything on the topic.

Physics students are taught that there are 3 laws of motion. In simplified form let’s list them as:

1. Inertia

2. F=ma

3. Action-reaction

What I’m proposing here is that there are only 2 laws of motion. I don’t want people to get too freaked out here, but it’s quite clear to me that there are only 2. The 2nd law and the 3rd law. The first law, what is that? The first law is simply an incomplete statement of the 2nd law. In no other equation do you get two for the price of one. I guess it’s just due to the respect owed Newton, but that’s no reason to keep superfluous laws floating about.

To illustrate, we have Hooke’s law, which states that F=-kx. Imagine if I said that was Hooke’s 2nd law, and  Hooke’s first law is thus:

“A spring with no force on it has no displacement, and a spring with a constant displacement must have a constant force on it.”

Any reasonable person would say, well that’s what the equation says, duh. They’re the same thing, except the equation expresses the relationship completely.

Now, I read somewhere that the first law actually details what an inertial frame of reference is, which essentially means a viewpoint from which there are no external forces. This seems rather tautological to me. Like saying:

“People who have more birthdays live longer.”

No kidding.

 

 


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