Scientific and Technological Knowledge: The "Three Laws of Newton" in Life

In recent years, in the examination of public institutions, the frequency and difficulty of basic science examination points in the science and technology sector have increased. In the three subjects of basic science, the first subject to be learned is physical knowledge, when it comes to physical knowledge, we have to mention classical mechanics, so today I will introduce you to the three laws of Newtonian motion in classical mechanics.

Newton's laws of motion: Newton's first law, Newton's second law, Newton's third law.

[Newton's first law] is also known as the law of inertia, any object must maintain a uniform linear motion or rest state, until the external force forces it to change the state of motion.

[Newton's second law] The magnitude of the acceleration of the object is proportional to the force, inversely proportional to the mass of the object, and proportional to the reciprocal of the mass of the object, and the direction of acceleration is the same as the direction of the force.

Newton's Third Law: The forces and reactions between two interacting objects are always equal in magnitude and opposite directions, acting on the same straight line.

Let's take a look at some of the cases in life that embody Newton's three laws.

Newton's first law, also known as the law of inertia, is very close to our daily lives, with both favorable and unfavorable sides. First of all, let's first understand the favorable cases that can reflect Newton's first law in daily life, such as: the greater the speed of the long jumper, the better the long jump performance; After the bullet leaves the muzzle, it is still able to continue to fly forward; With force, you can throw the stone far away or splash the water inside the basin. Of course, there are also many unfavorable cases, such as: jumping from a moving car, people are easy to fall and get injured; Fast-moving electric vehicles hit the guardrail, and the people on the car will fly out of the air due to inertia; When the car starts or accelerates suddenly, the people in the car will fall down one after the other.

Newton's second law, which mainly studies the magnitude and direction of acceleration. What is acceleration, that is, the physical quantity of speed changing in a certain direction, that is, the rate of increase in speed per second when the object is moving. There are also many cases in life, for example, the heavier the car, the greater the engine horsepower; To achieve the same starting speed, the heavier the object, the greater the pulling force required.

Newton's third law, which mainly studies the relationship between force and reaction force, is equal in size but in opposite directions. There are also many common cases in life that embody Newton's third law, such as: paddle backwards, water pushes the paddle forward; Jets spew high-temperature and high-pressure gas backwards, and air pushes the air forward; If you punch someone else, your own fist will also feel pain.

In the process of investigation, most of the comprehension type test questions appear, and a case will be given, and the question reflects Newton's first laws.

【Exercise Questions】

The seats of the sedan not only have backrests, but also headrests. The role of the headrest is to protect the person's cervical spine from harm when the back of the car is violently hit, which reflects which law. ( )

a. Newton's first law

b. Newton's second law

c. Newton's third law

d. The law of universal gravitation

【Zhonggong Answer】a. Analysis: When the car suddenly starts or is violently hit, the lower body of the driver and the passenger moves rapidly with the car, and the upper body still has to maintain the original state of motion due to inertia, so the head falls backwards, at this time, the safety headrest can effectively prevent the harm caused by inertia. This belongs to Newton's first law, the law of inertia. It has nothing to do with Newton's second and third laws and the law of universal gravitation. Therefore, the answer to this question is a.

I hope that you can have a preliminary understanding of the content of basic science, especially classical mechanics, and how to investigate it in this article.

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