School Encyclopedia. What is weightlessness Weightlessness from the point of view of physics

Weight as the force with which any body acts on a surface, support or suspension. There is weight due to the gravitational attraction of the Earth. Numerically, the weight is equal to the force of gravity, but the latter is applied to the center of mass of the body, while the weight is applied to the support.

Weightlessness - zero weight, can occur if there is no gravitational force, that is, the body is sufficiently away from massive objects that can attract it.

The International Space Station is located at a distance of 350 km from the Earth. At this distance, the gravitational acceleration (g) is 8.8 m/s2, which is only 10% less than on the surface of the planet.

In practice, you rarely see - the gravitational effect always exists. Astronauts on the ISS are still affected by the Earth, but weightlessness is present there.

Another case of weightlessness occurs if gravity is compensated by other forces. For example, the ISS is subject to gravity, slightly reduced due to distance, but also the station moves in a circular orbit with the first cosmic velocity and the centrifugal force compensates for gravity.

Weightlessness on Earth

The phenomenon of weightlessness is also possible on Earth. Under the influence of acceleration, the weight of the body can decrease, and even become negative. The classic example given by physicists is a falling elevator.

If the elevator moves down with acceleration, then the pressure on the floor of the elevator, and, consequently, the weight, will decrease. Moreover, if the acceleration is equal to the acceleration of free fall, that is, the elevator falls, the weight of the bodies will become zero.

Negative weight is observed if the acceleration of the elevator exceeds the acceleration of free fall - the bodies inside "stick" to the ceiling of the car.

This effect is widely used to simulate weightlessness in the training of astronauts. An aircraft equipped with a training chamber rises to a considerable height. After that, it dives down along a ballistic trajectory, in fact, the machine levels off at the surface of the earth. When diving from 11 thousand meters, you can get 40 seconds of weightlessness, which is used for training.

There is a misconception that such perform complex figures, like the "Nesterov loop", to obtain weightlessness. In fact, modified serial passenger aircraft are used for training, which are incapable of complex maneuvers.

physical expression

The physical formula for the weight (P) during the accelerated movement of the support, whether it be a falling bodice or a diving aircraft, is as follows:

where m is the body weight,
g is the free fall acceleration,
a is the support acceleration.

When g and a are equal, P=0, that is, weightlessness is achieved.

We are used to the fact that all objects around us have weight. This happens because the force of gravity attracts them to the Earth. Even if we are flying in an airplane or skydiving, the weight does not disappear from us. But what happens if the weight still disappears, when does this happen, and what interesting phenomena are observed under weightlessness? All this is in this post.

The law of universal gravitation, discovered by Newton, states that all bodies with mass are attracted to each other. For bodies with a small mass, such an attraction is practically not noticeable, but if the body has a large mass, such as our planet Earth (and its mass in kilograms is expressed in 25-digit numbers), then the attraction becomes noticeable. Therefore, all objects are attracted to the Earth - if they are lifted, they fall down, and when they fall, gravity presses them to the surface. This leads to the fact that everything on Earth has weight, even air is pressed against the Earth by gravity and with its weight presses on everything that is on its surface.

When can the weight disappear? Either when gravity does not act on the body at all, or when it does, but nothing prevents the body from falling freely. Although the force of attraction to it decreases with distance from the Earth, even at an altitude of hundreds and thousands of kilometers it remains strong, so getting rid of gravity is not easy. But it is quite possible to be in a state of free fall.

For example, you can find yourself in a state of weightlessness if you find yourself in an airplane moving along a special trajectory - just like a body that would not be hindered by air resistance.

It all looks like this:

Of course, the plane cannot move along such a trajectory for a long time, because it will crash into the ground. Therefore, only astronauts living on the orbital station face a long stay in weightlessness. And they have to get used to the fact that many of the phenomena we are accustomed to in weightlessness occur in a completely different way than on Earth.

1) In weightlessness, you can easily move heavy objects and move yourself with only a little effort. True, for the same reason, any objects must be specially fixed so that they do not fly around the orbital station, and for the duration of sleep, astronauts climb into special bags attached to the wall.

It takes time to learn how to move in zero gravity, and beginners do not succeed immediately. “They push with all their might and hit their heads, get tangled in wires and stuff, so this is a source of endless fun,” one of the American astronauts said on this topic.

2) Liquids in weightlessness take a spherical shape. Water will not work, as we are used to on Earth, stored in an open container, poured out of a kettle and poured into a cup, even washing our hands will not work in the usual way for us.

3) The flame under weightless conditions is very weak and fades with time. If you light a candle under normal conditions, it will burn brightly until it burns out. But this happens because the heated air becomes lighter and rises, making room for fresh air saturated with oxygen. In weightlessness, air convection is not observed, and over time, the oxygen around the flame burns out and combustion stops.

Burning a candle under normal conditions and in zero gravity (right)

But a constant supply of oxygen is needed not only for combustion, but also for breathing. Therefore, if the astronaut is motionless (for example, sleeping), then a fan must operate in the compartment to mix the air.

4) In zero gravity it is possible to obtain unique materials that are difficult or even impossible to obtain under terrestrial conditions. For example, ultra-pure substances, new composite materials, large regular crystals, and even drugs. If it were possible to reduce the cost of delivering goods to orbit and back, this would solve many technological problems.

5) In weightlessness aboard the orbital station, some previously unknown effects were discovered for the first time. For example, the formation of structures resembling crystalline ones in plasma, or the "Dzhanibekov effect" - when a rotating object suddenly changes the axis of rotation by 180 degrees at certain intervals.

Dzhanibekov effect:

6) Weightlessness has a significant impact on humans and living organisms. Although it is possible to adapt to life in zero gravity, it is not so easy to do so. Being in a state of weightlessness for the first time, a person loses orientation in space, dizziness occurs, since the vestibular apparatus stops working normally. Other changes in the body include redistribution of fluid in the body, due to which the face swells and stuffy nose, due to the loss of load on the spine, growth increases, and with prolonged exposure to weightlessness, muscles atrophy and lose bone strength. To reduce negative changes, astronauts have to regularly perform special exercises.

After returning to Earth, astronauts have to adapt to the old conditions again, not only physically, but also psychologically. They may, for example, habitually leave a glass in the air, forgetting that it will fall.

"Physics of weightlessness". Astronauts on the ISS tell how the laws of physics work in weightlessness:

Weightlessness

Astronauts aboard the International Space Station

Candle burning on Earth (left) and in zero gravity (right)

Weightlessness- a state in which the force of interaction of the body with the support (body weight), arising in connection with gravitational attraction, the action of other mass forces, in particular the force of inertia arising from the accelerated movement of the body, is absent. Sometimes you can hear another name for this effect - microgravity. This name is incorrect for near-Earth flight. Gravity (the force of attraction) remains the same. But when flying at great distances from celestial bodies, when their gravitational influence is negligible, microgravity really arises.

To understand the essence of weightlessness, one can consider an aircraft flying along a ballistic trajectory. Such methods are used to train astronauts in Russia and the United States. In the cockpit, a weight is suspended on a thread, which usually pulls the thread down (if the aircraft is at rest or moves evenly and in a straight line). When the thread on which the ball hangs is not stretched, a state of weightlessness takes place. Thus, the pilot must control the aircraft so that the balloon is suspended in the air, and the thread is not taut. To achieve this effect, the aircraft must have a constant downward acceleration g. In other words, pilots create zero G. For a long time, such an overload (up to 40 seconds) can be created by performing a special aerobatics maneuver (which has no name other than "failure in the air"). Pilots abruptly apply for a decrease in altitude, with a standard flight altitude of 11,000 meters, this gives the required 40 seconds of "weightlessness"; inside the fuselage there is a chamber in which future cosmonauts train; it has a special soft coating on the walls to avoid injuries during climb and drop. A person experiences a similar feeling of weightlessness when flying civil aviation flights during landing. However, for the sake of flight safety and a heavy load on the aircraft structure, civil aviation drops altitude by making several long spiral turns (from a flight altitude of 11 km to an approach altitude of about 1-2 km). Those. the descent is made in several passes, during which the passenger feels for a few seconds that he is lifted up from the seat. (The same feeling is familiar to motorists who are familiar with tracks passing through steep hills when the car starts to move down from the top) Claims that the aircraft performs aerobatics such as "Nesterov's loop" to create short-term weightlessness is nothing more than a myth. Training is performed in slightly modified commercial passenger or cargo class aircraft, for which aerobatics and similar flight conditions are supercritical and can lead to destruction of the aircraft in the air or rapid fatigue failure of supporting structures.

Features of human activity and the work of technology in weightlessness

Under conditions of weightlessness on board a spacecraft, many physical processes (convection, combustion, etc.) proceed differently than on Earth. The absence of gravity, in particular, requires a special design of systems such as showers, toilets, food heating systems, ventilation, etc. To avoid the formation of stagnant zones where carbon dioxide can accumulate, and to ensure uniform mixing of warm and cold air, the ISS, for example, has a large number of fans installed. Eating and drinking, personal hygiene, working with equipment and, in general, ordinary everyday activities also have their own characteristics and require the astronaut to develop habits and the necessary skills.

The influence of weightlessness is inevitably taken into account in the design of a liquid propellant rocket engine designed to be launched in weightlessness. Liquid fuel components in tanks behave exactly like any liquid (form liquid spheres). For this reason, the supply of liquid components from the tanks to the fuel lines may become impossible. To compensate for this effect, a special design of tanks is used (with separators for gas and liquid media), as well as a procedure for settling fuel before starting the engine. Such a procedure consists in turning on the auxiliary engines of the ship for acceleration; the slight acceleration created by them precipitates liquid fuel on the bottom of the tank, from where the supply system directs the fuel into the lines.

The impact of weightlessness on the human body

During the transition from the conditions of terrestrial gravity to the conditions of weightlessness (first of all, when the spacecraft enters orbit), the majority of astronauts experience an organism reaction called space adaptation syndrome.

With a long (several weeks or more) stay of a person in space, the absence of gravity begins to cause certain changes in the body that are of a negative nature.

The first and most obvious consequence of weightlessness is the rapid atrophy of the muscles: the muscles are actually turned off from human activity, as a result, all the physical characteristics of the body fall. In addition, the consequence of a sharp decrease in the activity of muscle tissues is a reduction in the body's consumption of oxygen, and due to the resulting excess of hemoglobin, the activity of the bone marrow that synthesizes it (hemoglobin) may decrease.

There is also reason to believe that the restriction of mobility will disrupt the phosphorus metabolism in the bones, which will lead to a decrease in their strength.

Weight and gravity

Quite often, the disappearance of weight is confused with the disappearance of gravitational attraction. This is wrong. An example is the situation on the International Space Station (ISS). At an altitude of 350 kilometers (the altitude of the station), the acceleration of gravity is 8.8 / ², which is only 10% less than on the surface of the Earth. The state of weightlessness on the ISS does not arise due to the “lack of gravity”, but due to movement in a circular orbit with the first cosmic velocity, that is, astronauts, as it were, constantly “fall forward” at a speed of 7.9 km / s.

Weightlessness on Earth

On Earth, for experimental purposes, a short-term state of weightlessness (up to 40 s) is created when an aircraft flies along a parabolic (and in fact - ballistic, that is, one along which an aircraft would fly under the influence of gravity alone; this trajectory is a parabola only when small speeds of movement; for a satellite it is an ellipse, a circle or a hyperbola) trajectories. The state of weightlessness can be felt at the initial moment of free fall of a body in the atmosphere, when the air resistance is still small.

Links

• Astronomical Dictionary Sanko N.F.
• Weightlessness parabola Video by Roscosmos TV studio

Notes

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Synonyms:

See what "Weightlessness" is in other dictionaries:

Weightlessness… Spelling Dictionary

Lightness, ethereality, weakness, hydroweightlessness, insignificance, airiness Dictionary of Russian synonyms. weightlessness, see lightness 1 Dictionary of synonyms of the Russian language. Practical guide. M.: Russian language. Z. E. Alexandrova ... Synonym dictionary

A state in which external forces acting on a body do not cause mutual pressures of its particles on each other. In the Earth's gravitational field, the human body perceives such pressures as a feeling of weight. Weightlessness occurs when ... ... Big Encyclopedic Dictionary

Modern Encyclopedia

WEIGHTLESSNESS, a state experienced by an object in which the effect of weight is not manifested. Weightlessness can be experienced in space or during free fall, although there is a gravitational attraction of a “weighty” body. Astronauts ... ... Scientific and technical encyclopedic dictionary

The state of a material body moving in a gravitational field, in addition, the forces of gravity acting on it or the movement it makes do not cause pressures between the bodies. If a body is at rest in the Earth's gravitational field on a horizontal plane, ... ... Physical Encyclopedia

Weightlessness- WEIGHTLESSNESS, a state in which external forces acting on a body do not cause mutual pressures of its particles on each other. Weightlessness occurs when a body moves freely in a gravitational field (for example, during a vertical fall, movement along ... ... Illustrated Encyclopedic Dictionary

To the question what is weightlessness? under what conditions does it occur? given by the author Marty_Ray_ka the best answer is Weightlessness is the state of a body when only gravitational forces act on it, and the external gravitational field does not cause pressure of one part of the system on another and their deformation. In a state of weightlessness, the metabolism and blood circulation of a living organism change somewhat. Weightlessness arises in the free fall of a body and in spacecraft when they move with the engines turned off.

Answer from Phantom[guru]
when the body has no weight. either in space or in free fall, the body is in zero gravity.

Answer from Komerrsant[guru]
Weight - the force with which the body acts on any support, which means weightlessness, (in your own words) this is the state of the body when it does not put pressure on the support. If there is not enough information in the wiki, look

Answer from User deleted[guru]
Weightlessness is a state when the force of interaction of a body with a support (body weight), arising in connection with gravitational attraction, the action of other mass forces, in particular the force of inertia arising from the accelerated movement of the body, is absent. Sometimes you can hear another name for this effect - microgravity - but this name is incorrect! ! - gravity (force of attraction) remains the same.
Quite often, the disappearance of weight is confused with the disappearance of gravitational attraction. This is wrong. An example is the situation on the International Space Station (ISS). At an altitude of 350 kilometers (the altitude of the station), the free fall acceleration is 8.8 m/s², which is only 10% less than on the Earth's surface. The state of weightlessness on the ISS arises due to movement in a circular orbit with the first cosmic velocity.
On Earth, for experimental purposes, a short-term state of weightlessness (up to 40 s) is created when an aircraft flies along a parabolic (and in fact - ballistic, that is, one along which an aircraft would fly under the influence of gravity alone; this trajectory is a parabola only when small speeds of movement; for a satellite it is an ellipse, a circle or a hyperbola) trajectories. The state of weightlessness can be felt at the initial moment of free fall of the body in the atmosphere, when the air resistance is still small.
To understand the essence of weightlessness, one can consider an aircraft flying along a ballistic trajectory. These are used to train astronauts in Russia and the United States. In the cockpit, a weight is suspended on a thread, which usually pulls the thread down (if the aircraft is at rest or moves evenly and in a straight line). When the thread on which the ball hangs is not stretched, a state of weightlessness takes place. Thus, the pilot must control the aircraft so that the balloon is suspended in the air, and the thread is not taut. To achieve this effect, the aircraft must have a constant downward acceleration g. Thus, we can say that the plane "falls" along with the ball, thread, pilot and astronauts.
[edit]
Weight and its perception
Weightlessness is the state of a body when it is under the action of only mass forces. For example, under the influence of only gravity. Motion under the influence of gravity alone is also called free fall.
If, in addition to body forces, surface forces act on the body, for example, the support reaction, a state of weightiness arises.
Body weight is the force with which a body acts on a support or suspension.
What people perceive as weight is only a consequence of the impact on their bodies of the reaction of the support or environment.
The force acting on different parts of the body located on the Earth is not the same. If we conditionally divide the body into horizontal layers, then we can imagine that, in addition to the reaction of the underlying support, each layer will also be affected by pressure from the layers located above. A person feels a similar pressure difference, like weight.
A body placed in a hermetically sealed container experiences a state of weightlessness during experiments with free fall (for example, dropped from a high tower). This happens because the acceleration of the container, the air contained inside it, and all parts of the body itself, caused by the action of gravity, is the same, the support reaction and the pressure gradient are absent (in the case of a free fall of the body outside the container, this is not entirely true, except for the force of gravity on it there is also a reaction of the external environment - the force of air resistance).

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PURPOSE: To give the concept of weightlessness in a complex form OBJECTIVES: To understand the mechanism of the occurrence of this phenomenon; Describe this mechanism mathematically and physically; Tell some interesting facts about weightlessness; To understand how the state of weightlessness affects the health of people in a spacecraft, on a station, etc., that is, to look at weightlessness from a biological and medical point of view.

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Body weight - the force with which the body, due to its attraction to the ground, acts on a support or suspension. According to Newton's III law: Р = -Fу (1) (Fig. 1); 2) Also, according to Newton's III law Fт = -Fу (2); 3) Comparing expressions 1 and 2, we get: Р = FT; 4) According to Newton's II law, when a body of mass m moves under the action of gravity Ft and elastic force FY with acceleration a, the equality is fulfilled: FT + FY = ma 5) From the equations P = -FY and Ft + Fy = ma we get: P = Ft - ma \u003d mg - ma, or P \u003d m (g - a). 6) OY (Fig. 2): Ru = m(gY - aY) or P = m(g - a).

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Four cases of body weight in a rapidly moving elevator

When talking about body weight in a rapidly moving elevator, three cases are usually considered: The elevator moves with an upward acceleration (P>mg, P=mg+a) The elevator moves with a downward acceleration (P

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And how should the elevator move so that a person can walk on the ceiling? The elevator must move with an acceleration greater than g. When the acceleration a becomes equal to g, the weight becomes equal to zero. If you continue to increase the acceleration, then we can assume that the weight of the body will change direction.

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WEIGHTLESSNESS If the body, together with the support, falls freely, then a = g, and from the formula P = m(g – a) it follows that P = 0. The disappearance of weight when the support moves with the acceleration of the total fall is called weightlessness. There are two types of weightlessness: Static weightlessness - weight loss that occurs at a great distance from celestial bodies due to the weakening of attraction. 2) Dynamic weightlessness - the state in which a person is during a flight in orbit.

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The emergence of dynamic weightlessness

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A body under the action of external forces will be in a state of weightlessness if: 1) The forces acting on the body are only mass (gravitational forces); The field of these body forces is locally homogeneous; The initial velocities of all particles of the body are the same in modulus and direction.

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Flame in weightlessness In weightlessness, the flame of a candle takes on a spherical shape and has a blue color Candle flame on Earth Flame in weightlessness

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Boiling a liquid in zero gravity In zero gravity, boiling becomes a much slower process. However, the vibration of the liquid can cause it to boil violently. This result has implications for the space industry. Boiling water on Earth Boiling water in zero gravity

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MAN AND WEIGHTLESSNESS Ways to solve problems associated with weightlessness: Muscle training, muscle electrical stimulation, negative pressure applied to the lower half of the body, pharmacological and other means; Creation of artificial gravity on board the spacecraft; Limitation of muscle activity, deprivation of a person's habitual support along the vertical axis of the body, decrease in hydrostatic blood pressure, etc.

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Study of life problems in space American orbital station Skylab (from the English Skylab, that is, sky laboratory - "sky laboratory")

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Operation in zero gravity French doctors led by Professor Dominique Martin from Bordeaux performed the world's first surgical operation in zero gravity. The experiment was carried out on board the A-300 airliner in a specially equipped module. It involved three surgeons and two anesthesiologists, who were to remove a fatty tumor on the arm of a patient, a volunteer, 46-year-old Phillip Sancho, under weightless conditions.

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Results Weightlessness arises when a body falls freely together with a support, i.e. the acceleration of the body and the support is equal to the acceleration of free fall; Weightlessness is of two types: static and dynamic; Weightlessness can be used to implement some technological processes that are difficult or impossible to implement under terrestrial conditions; The study of a flame under weightless conditions is necessary for assessing the fire resistance of a spacecraft and for developing special fire extinguishing means;

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Summary A detailed understanding of liquid boiling in space is critical to the successful operation of spacecraft carrying tons of liquid propellant; The impact of weightlessness on the body is negative, as it causes a change in a number of its vital functions. This can be corrected by creating artificial gravity on the spacecraft, limiting the astronauts' muscular activity, etc.; A person can be operated on in outer space, under conditions of weightlessness. This was proved by French doctors led by Professor Dominique Martin from Bordeaux.

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