Introduction to physics 1
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Physical method-the definition of physical physics
Physics is called physics for short.
Europe? Physics? The word originally comes from Greek, which means nature.
What did Europeans call physics in ancient times? Natural philosophy? .
summary
Physics is a natural science, which mainly studies matter and its motion in time and space, as well as all related concepts, including energy and action.
More broadly, physics is the study and analysis of nature, with the purpose of understanding the behavior of the universe.
Physics is one of the oldest subjects.
In the past two thousand years, physics has often been confused with philosophy and chemistry.
It was not until the scientific revolution in the 16th century that it became a modern science alone.
Now, physics has become one of the most basic subjects in natural science.
Physical theory is usually expressed in mathematical form.
The laws of physics verified by a large number of rigorous experiments are called laws of physics.
However, like many other natural science theories, these laws cannot be proved, and their correctness can only be tested through repeated experiments.
The influence of physics is far-reaching, because the breakthrough of physics often leads to the emergence of new technologies, and the new ideas of physics can easily be introduced to other academic fields.
For example, the progress in electromagnetism directly led to the emergence of new products such as television, computers and household appliances, which greatly improved the living standards of the whole society; The success of nuclear fission makes nuclear power generation no longer a dream.
Take a roller coaster and understand physics II.
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We have all been to amusement parks and are no strangers to roller coasters.
Most roller coasters can accommodate 2, 4, 6 or 8 people per car. These carriages are connected with each other by hooks, just like trains, running along winding tracks.
Because the track is winding, the thrill and excitement also make many people excited and fascinated.
In fact, riding a roller coaster not only allows us to experience the feeling of adventure and excitement, but also allows us to better understand many principles in physics.
After the roller coaster started, it was driven by a mechanical device to push the car to the highest point, but after the first trip, there was no mechanical device to provide power.
Perhaps you will be curious, what does that car rely on for the following operations? In fact, the driving force behind the car is gravitational potential energy, which is the process of constant transformation between gravitational potential energy and kinetic energy.
Tell me specifically how it was transformed.
First of all, what is gravitational potential energy? Generally speaking, gravitational potential energy is the energy possessed by the position and height of an object and the acceleration generated by gravity.
Then at first, the roller coaster rises a little by the power provided by the mechanical device, and at the same time, the gravitational potential energy of the roller coaster also increases a little. When the roller coaster is at the highest point, the gravitational potential energy reaches the maximum.
When the roller coaster begins to descend, due to the decrease of height, the gravitational potential energy is decreasing in this process.
According to the law of conservation of energy, energy will neither disappear nor be generated. It just changes from one form to another, or from one object to another. In this process of transformation or transfer, its total energy is constant.
Here, the reduced gravitational potential energy is converted into kinetic energy.
And this kinetic energy is the driving force for the roller coaster to continue running.
Has the reduced potential energy been converted into kinetic energy? Actually, it's not. There is friction between the wheels of a roller coaster and the track. Friction will produce heat, and heat energy will lose some kinetic energy and potential energy.
This converted kinetic energy can't push the roller coaster to the previous height.
This is why the slope behind the roller coaster is smaller than the original slope.
Let's take a look at the excitement brought by the roller coaster and what kind of physical principles are embodied.
First of all, understand that the most exciting car on the roller coaster is in the back.
Because gravity acts on the center of mass in the middle of the roller coaster, the last car reaches and passes the highest point faster than the previous car.
In this way, passengers will have a feeling of being thrown out.
If the wheels of the following car are not firmly fixed on the track, it is very likely that an accident will occur, that is, the last car may derail and be thrown out when it reaches or passes the highest point.
So, if you want to be more exciting, sit behind the roller coaster.
Why isn't the front car like this? Because its center of mass is behind, although it falls for a short time, it will not be pushed by gravity until the center of mass crosses the high point.