Inertia refers to the property that an object remains in a static state or a state of uniform linear motion, and inertia is an inherent property of an object.

When people jump on the train, the train and people are separated, but due to inertia, people have the same initial speed and the same direction as the train at the moment of jumping, and the distance traveled by people and trains is the same during the flight time, so when people land, people will still fall in the same position.

The same position mentioned here is only relative to people and trains. When people and trains are regarded as a whole, this position has changed relative to other reference objects (such as railway tracks), rather than the original position.

Extended data:

Einstein and relativity explain inertia;

An important progress in understanding inertia is the relationship between inertia and energy.

Albert Einstein put forward the special theory of relativity in 1905' s paper "On electrodynamics of moving objects", which is a brand-new physical theory based on the inertia and inertial reference system developed by Galileo and Newton. It unifies the theories of mechanics and electromagnetism and brings about a fundamental change in the concept of time and space.

Einstein then proved the mass-energy relationship, E=mc? A certain mass corresponds to a certain energy, and a certain energy corresponds to a certain mass.

The energy here includes various forms of energy, which breaks through the above understanding of linking some form of energy with inertia. In this way, inertia is the property of energy, and energy has inertia (mass), and any inertial mass should be attributed to energy.

As the basic concept of physics and the quantity of matter, the concept of quality has been relegated to a secondary position. In modern physics, the concepts of energy and momentum are much more important than those of mass and force.

Although this epoch-making theory actually changed many Newton's concepts, such as mass, energy and distance, Einstein's concept of inertia was no different from Newton's original concept after that. In fact, the whole theory is based on Newton's definition of inertia. But it also makes the relativity principle of special relativity only applicable to inertial reference frame.

In this frame of reference, objects that are not affected by external forces must remain stationary or move in a straight line at a uniform speed.

Another profound result of special relativity is that energy and mass are not unrelated physical properties, but can be transformed into each other. This brand-new relationship also gives the concept of inertia a new meaning. The logical result of special relativity is that if mass obeys the principle of inertia, then energy must also obey the principle of inertia. In many cases, this theory greatly broadens the definition of inertia and can be applied to matter and energy.

Energy has inertia, which broadens the understanding of inertia and energy. Its great practical value is the release of nuclear energy.

In the fission reaction, the rest mass of fission products is less than that of substances before fission, and mass defects release a lot of fission energy. In the fusion reaction, the net mass of fusion products is less than that of materials before fusion, and mass defects release a lot of fusion energy. It also makes people have a good understanding of many physical phenomena, including the generation and annihilation process of positive and negative particle pairs involving the transformation of all mass and energy of matter.

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