Why do weightless people float up, why do weightlessness occur

Completely weightless. There are two situations, one is when the gravity is zero (as in space), and then floating is obvious.

There is also a case of free fall.

, the gravitational force is fully accelerating.

form manifested. That's when people float up.

The situation you are talking about is the second.

The specific reasons are:

There are two kinds of effects of force, one is manifested as motion, i.e., acceleration, and the other is manifested as force deformation, i.e., force such as support force. Whether people can float up depends on whether people can stand on the ground, that is, whether the ground has support for people. When a person is in a box in free fall, the acceleration of the person is g, and the net force experienced by the person is the force of gravity.

At this time, gravity is all acting on the aspect that gives people acceleration, and there is no need for a support force to make people feel like they are standing on the ground. If there is a random force, it destroys this state of motion of the person (acceleration in the direction of gravity), and the person swayed, that is, the feeling of floating. But at this time, the person's float refers to the frame of reference relative to this box.

The floating, human and entire box together is in free fall.

Weightlessness is equivalent to the force of gravity that is counteracted, and we do not have to rely on the support provided by the ground to maintain balance. Then, we can float up.

Gravity fully provides the acceleration of the system, which is equivalent to no gravity from the system.

In life, overweight and weightlessness are very common, for example, when people are in the elevator, when the elevator accelerates up, they feel that the pressure on the soles of the feet of the elevator increases, which is the phenomenon of overweight.

In order to reduce the pressure on the bridge, the bridge generally causes a convex shape, so that the car has a downward acceleration when crossing the bridge and the pressure on the bridge is reduced, when the car passes through the sunken road surface, due to the vertical upward acceleration and the phenomenon of overweight, often make the car tire burst due to the high pressure.

Due to gravity, on the ground, the balls made with modern technology are not absolutely spherical, which is one of the important reasons for the wear of the bearings, if in the spacecraft can be made of absolutely spherical balls, and the astronaut in the spacecraft due to complete weightlessness, so his diet, life methods must be very different from the ground. Overweight and weightlessness are two opposite concepts, so I'll explain them to you together.

There is an object that we assume to have a mass of mNow, this object is moving vertically upwards (i.e., in the direction of leaving the Earth) with acceleration a. Obviously, because of this motion, the pressure n on the horizontal support surface (or the tension t on the vertical hanging line) is greater than the weight of the object itself, which should be equal to m(g+a).

This phenomenon is called overweight. We often say that the object is overweight

Similarly, now, if the object moves vertically downward (i.e., in the direction of the Earth) with acceleration a, the pressure n (or tension t) described above is less than the weight of the object itself, which should be equal to m(g-a).This phenomenon is called weightlessness. We often say that the object is weightless

If a = g, then the object is in fact in free fall, the pressure n (or tension t) is zero, and we say that the object is completely weightless

For example, an object in a satellite that moves in a uniform circular motion around the Earth has zero pressure on the satellite's floor because its vertical downward acceleration a is the gravitational acceleration g at the position of the satellite.

Of course, in daily life, we can also experience overweight and weightlessness. For example, in an elevator, we can go through the process of being overweight and weightless. When the elevator starts to ascend, we are overweight at this point as we have an upward acceleration along with the elevator.

On the contrary, when the elevator starts to descend, we are weightless at this point as we have a downward acceleration along with the elevator. If the elevator breaks down, we will fall down with the elevator. We must be completely weightless at this point.

However, of course, we would rather not have such an experience.

Man is subjected to gravitational force on the earth, and gravitational force is the vector sum of centripetal force and gravity, when gravitational force is completely provided by centripetal force, gravity disappears. The total weightlessness created by man is by turning the gravitational force into a completely centripetal force

Conditions for the occurrence of weightlessness: when the object does a downward acceleration motion or an upward deceleration motion, the object is in a weightless state, that is, no matter how the object moves, as long as it has a downward acceleration, the object is in a weightless state.

When the elevator is stationary, the elevator gives people the support force of the gravity that the person receives, and the person will not lose weight. When the elevator begins to accelerate down (start), both people and the elevator do downward acceleration motion, and the acceleration of people's acceleration is provided by the gravity of people, therefore, the support force received by people at this time is less than gravity, and people obviously feel that they have become lighter, in fact, they are weightless. Elevators don't accelerate to the point where they're completely weightless.

When the elevator is driven up to its working speed (when it moves at a constant speed), the person is weightless again. When the elevator starts to brake (stop the process), the person has to do a downward deceleration movement, at this time the force to be borne by the human foot in addition to the person's own gravity, but also to provide the force needed to decelerate, so at this time you feel that you have become heavier, this is overweight.

First of all, it is explained that "weightlessness" in space is not weightlessness in the true sense. Rather, it is a special form of hunger similar to weightlessness.

The definition of weightlessness is a phenomenon in which the pressure of an object on a support is less than the gravitational force experienced by the object. If you think about it carefully, you will find that this definition sets a premise for the phenomenon of weightlessness, that is, the existence of a gravitational field. Without a gravitational field, there is no gravity, and there is no weightlessness.

In other words, according to this definition, weightlessness only occurs within the gravitational pull of celestial bodies. For space without a gravitational field (which is negligible or equilibrium with centrifugal acceleration, it is all included in the absence of a gravitational field), there is no weightlessness according to the above definition due to the absence of gravity. The state without gravity in the spacecraft scum is also customarily called weightlessness because it feels similar to weightlessness.

The state of "weightlessness" in space is a state of detachment from the force field, or the state of complete absence of gravity. This is known from the situation of the astronaut levitating on the spacecraft.