# Are Newton's laws of motion redundant?

• V0ODO0CH1LD
In summary, there is some debate about whether Newton's three laws of motion are truly separate observations or if they can be summarized in a single equation. However, looking at the original text of Newton's work, it is clear that each law is distinct and conveys a different concept. While some may argue that the first law can be derived from the second, it is important to consider the original intention behind each law in order to fully understand their significance.
V0ODO0CH1LD
My question has to do with something Leonard Susskind, a professor of theoretical physics at Stanford University and director of the Stanford Institute for Theoretical Physics, said in one of his lectures. Basically that he didn't know why Newton wrote three laws of motion, when they could all be summarized as $F=ma$.

I can see why you would think that of Newton's first two laws, seeing as they are the same observation: force is proportional to acceleration. But I can't say the same about the third law. Which states that, in a closed system, the center of mass suffers no acceleration.

Isn't the third law a separate/additional observation?

If he says so, then he is probably mistaken. I think if one law was direct consequence of another, Newton would notice and wrote so.

There are more approaches to formulate "Newton's laws", but the obligatory reading is what Newton wrote (Principia Mathematica):

http://archive.org/details/Newtonspmathema00newtrich

(see p. 83.)

As you can see from his book, each law says something different.

In modern physics the laws got reformulated a little bit, mainly due to new notion of inertial reference frame, but even after that, the Newton's laws are three separate statements.

Some people arrived at conclusions that the first law can be derived from the second, but I think this is only because they sticked to literal meaning of his or someone's else words and lost the original meaning Newton intended to transmit. I think that if more care and understanding were put into reformulation, it would be possible to restate the three laws in such way that would satisfy even a logician.

## 1. Are Newton's laws of motion still relevant today?

Yes, Newton's laws of motion are still relevant and used extensively in modern physics and engineering. They form the basis of classical mechanics and are essential in understanding and predicting the motion of objects.

## 2. Can Newton's laws of motion be applied to all objects?

Newton's laws of motion can be applied to most objects and situations, but they have their limitations. They work best for macroscopic objects and at speeds much slower than the speed of light. At the atomic and subatomic level, other laws such as quantum mechanics are needed to accurately describe motion.

## 3. Are Newton's laws of motion the only laws that govern motion?

No, there are other laws and principles that govern motion, such as the laws of thermodynamics and electromagnetism. However, Newton's laws of motion are fundamental and provide a general framework for understanding motion.

## 4. Can Newton's laws of motion be disproven?

New scientific discoveries and advancements may refine our understanding of Newton's laws of motion, but they have been extensively tested and have not been disproven. They have been validated by countless experiments and observations, making them a reliable framework for understanding motion.

## 5. Why are Newton's laws of motion still taught if they are redundant?

While Newton's laws of motion may seem redundant in the face of more complex theories and principles, they are still taught because they provide a solid foundation for understanding motion. They are also easier to comprehend and apply in everyday situations, making them a practical tool for solving problems in physics and engineering.

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