Newton s Three Laws Logic Loop, Newton s Third Law

Therefore, the best way to determine the inertial frame is.

Whether an object with it as a frame of reference remains at rest or moves in a straight line at a uniform speed when the resultant external force is zero;

Of course, there are some equivalent methods:

2) Look at whether this reference frame has a non-zero acceleration relative to another [inertial frame];

3) Look at whether the frame of reference itself is subjected to a non-zero resultant external force;

The fact that you chose the (3rd) method is an important reason for the so-called "cycle". Of course, you can't make a mistake with this method, the real problem is in the next two sentences:

To measure whether it is subjected to force, it is necessary to measure its acceleration;

What you mean by this is that the force is judged by acceleration, which is obviously the content of Newton's second law. But Newton's second law only works in inertial frames (and even more so Newton's first law, of course) – this is determined by the definition of the inertial frame (i.e., the first law) and the content of Newton's second law. So:

Your statement is only true in the frame of inertia;

And so: if we say "cycle", then there is already a "cycle" here, and there is no need for the first clause at all

To judge the inertial frame, you need to rely on force;

judgment needs to be based on the inertial frame;

But this is not the case: finding force based on acceleration (including in the case of zero acceleration) is only one way to calculate force – a method of finding force in an inertial frame. The more basic and general approach is:

1) the law of gravitation;

2) Newton's third law (law of action and reaction);

The law of gravitation is unique; Newton's third law is also irrelevant to inertial frames; So they can be used in any frame of reference. So, the basis you use to push out the loop is to mistake the sufficient condition for the necessary condition.

One more note: Newton.

1. The second law may be proposed earlier than the third law and the law of universal gravitation, but even so, that does not mean that the former is the basis and condition of the latter; It does not mean that the former is more universal and basic than the latter.

To measure its acceleration, an inertial frame is required;

This one is even more wrong. Before Newton, acceleration was a purely kinematic concept and had little to do with "force". It was Newton who used his second law to establish the relationship between acceleration and force in an inertial frame.

However, this does not mean that acceleration (or force) can only be determined (or meaningful) in an inertial frame.

The so-called "acceleration" is the "rate of change" of [velocity] in [time]. Its value depends on the determination of [Speed] and [Time]. Needless to say, the determination of velocity depends on the reference frame, so the determination of acceleration also depends on the reference frame - note that it is the reference frame, not the inertial frame.

These concepts and laws in classical mechanics, their logical relationship is like this:

Motion, frame of reference, velocity, acceleration;

Interaction (force) action and reaction (Newton's third law), the law of universal gravitation;

Newton's First Law (Law of Inertia) Inertial System Newton's Second Law (Relationship between Force and Acceleration);

Now, do you still think Newton's laws have logical loops?

The problem of the frame of reference is a major problem in history, such as the twin pretense or something, note that after the establishment of the theory of relativity, people began to examine the problem of the frame of reference (to be exact, the problem of the inertial frame and the non-inertial frame), specifically with the increase of learning, the landlord will slowly understand it, good luck.

Sentence 2 To determine whether an object is in an inertial frame, a frame of reference is determined.

To measure acceleration, it is also necessary to determine the reference frame first.

Interesting, I don't see the problem, and your statement makes a lot of sense.

Newton's third law: The action and reaction forces between two interacting objects are always equal in magnitude and opposite in direction, acting on the same straight line. This law was proposed by Isaac Newton in 1687 in his book Principles of Mathematics in Natural Philosophy.

Newton's third law of motion and the first.

The first and second laws together constitute Newton's laws of motion, which expound the basic laws of motion in classical mechanics.

Newton's third law of motion studies the mechanism of interaction between objects, and the object of study is at least two objects, and the interaction between more than two objects can always be distinguished into several pairs of objects that interact with each other.

Scope of application of Newton's third law.

Newton's third law of motion only applies to the interaction between physical objects in an inertial frame, for example, electrons moving in an electromagnetic field will be subjected to the electromagnetic field force, but there is no way to talk about the reaction force of electrons on the electromagnetic field; The inertial force in the non-inertial frame has no reaction force; The interaction with the participation of the field takes time to propagate, and the simultaneity of action and reaction does not hold. The third law is independent, but it also has a scope of application.

1. Between two objects, the action force and reaction force are reversed.

2. The action of force is mutual, appearing and disappearing at the same time.

3. It must be a force of the same nature.

4. The action force and the reaction force must act on both objects.

5. The action force can also be called the reaction force, and the two are relative.