Disclaimer: Created by middle school students for communication purposes only and not as a theoretical basis for learning.
The first compulsory course in high school physics describes Newton's second law as follows: the magnitude of the acceleration of an object is proportional to the force exerted on the object, inversely proportional to the mass of the object, and the direction of acceleration is the same as that of the force. This is Newton's second law.
If that's what Newton said, I'm going to deny Newton. Assuming that's what the editor said, I'm going to deny the editor.
Questions: The acceleration of an object is inversely proportional to the mass of the object, mass is an intrinsic property of the object, it is a constant independent of time and space position, since it is a constant, how can acceleration be inversely proportional to the mass of the object.
The magnitude of the acceleration of an object is directly proportional to the force exerted on the object, which is obviously one object, whereas the magnitude of acceleration is inversely proportional to the mass of the object, which is obviously two objects.
The editor's merging of two conclusions under different conditions into one conclusion is a misinterpretation of Newton's second law.
This conclusion was reached by the editors through such experiments, as shown in the figure.
In the question, add weights in the trolley, record the mass m of the trolley, measure the acceleration a, I would like to ask the editor, do weights have no mass?
The weight f does not change, the mass m of the trolley does not change, and the weight is added to the trolley, and the acceleration of the trolley is found to be smaller. It is then concluded that f is constant, and the mass m of the trolley is inversely proportional to the acceleration of the trolley. Shouldn't this be because the trolley is subjected to the gravity of the weights, causing the acceleration to become smaller? What does this have to do with the quality of the car? This is because under certain conditions of f, the acceleration of the trolley m is reduced under the action of the weight gravity, and it has nothing to do with the trolley m.
This is clearly a misrepresentation.
But according to the special theory of relativity, the faster the speed, the greater the mass.
where m is the mass of the object at velocity v, m0 is the rest mass of the object, and c is the speed of light in a vacuum.
This formula shows that when the velocity of an object approaches the speed of light, the mass increases accordingly. When the velocity is close to the speed of light, the value of the denominator is close to zero, causing the mass to tend to infinity. Therefore, the mass of an object under the theory of relativity is related to velocity.
It is true that from the point of view of special relativity, the mass of an object does change, but Newton is localized in that way
1) It is only suitable for objects moving at low speeds (the speed is lower than the speed of light);
2) It only applies to macroscopic objects, Newton's second law does not apply to microscopic particles;
3) The frame of reference should be an inertial frame, so Newton's second law should be described like this:The magnitude of the acceleration of the object is proportional to the force exerted on the object, and the direction of acceleration is the same as that of the force.
The acceleration of an object is inversely proportional to the mass of the object, which is derived from Newton's second law.
Another example is the problem described by the editor:
If the topic does not say that the mass and air resistance consumed during fuel combustion are ignored, then the calculated acceleration will not be accurate.
According to the law of gravitation, the minimum launch speed of a spacecraft is 79 km s (the object has to reach the speed of a circular motion around the Earth), assuming that the spacecraft is not considered when studying the air resistance, the spacecraft will not be successfully launched from the ground.
Ignore objective factors in high school physics: such as (2023 college entrance examination questions) ignore objective factors such as air resistance.
Such as similar similar problems:
In the same circuit, the current in the conductor is directly proportional to the voltage at both ends of the conductor and inversely proportional to the resistance of the conductor, which is Ohm's law.
In the same circuit, the current in the conductor is proportional to the voltage across the conductor. Here the conductor is the same conductor, i.e., the higher the voltage, the greater the current.
Inversely proportional to the resistance of the conductor, where the voltage is the same voltage, and the conductor is two or more different conductors.
Ask the editors how to combine the conclusions of different conditions compulsorily.
Both from a scientific point of view and from the editor's text, the formulation of Newton's second law and Ohm's law is wrong.
Disclaimer: Created by middle school students for communication purposes only.