Why does a state of weightlessness occur in space? What is weightlessness? The state of weightlessness on an artificial satellite is caused by

The weight of a body is the force with which the body, due to the attraction of the Earth, presses on a fixed (relative to the Earth) horizontal support or pulls the suspension thread. The weight of the body is equal to the force of gravity.

Since the support or suspension in turn acts on the body, then characteristic feature weightiness - the presence of deformations in the body caused by its interaction with a support or suspension.

When bodies fall freely, there are no deformations in them; in this case, the bodies are in state of weightlessness. The figure shows a setup that can be used to detect this. The installation consists of spring scales from which a load is suspended. The entire installation can move up and down on guides.

If the scales with the load fall freely, then the scale pointer is at zero, which means that the scale spring is not deformed.

Let's analyze this phenomenon using the laws of motion. Let us assume that a mass suspended on a spring moves downward with acceleration a. Based on Newton's second law, we can say that it is acted upon by a force that is equal to the difference between the forces P and F, where P is the force of gravity and F is the elastic force of the spring applied to the load. So,

ma = P - F or ma = mg - F

F = m (g - a)

When the load is in free fall, a = g and, therefore,

F - m (g - a) = 0

This indicates the absence of elastic deformations in the spring (and in the load).

The state of weightlessness occurs not only during free fall, but also during any free flight of a body when only gravity acts on it. In this case, the particles of the body do not act on the support or suspension and do not receive acceleration relative to this support or suspension under the influence of gravity towards the Earth.

If the installation shown in the figure is forced to move freely upward with a sharp tug on the rope, then the scale indicator will stand at zero during such a movement. And in this case, the scales and the load, moving upward with the same acceleration, do not interact with each other.

So, if only gravity acts on bodies, then they are in a state of weightlessness, a characteristic feature of which is the absence of deformations and internal stresses.

The state of weightlessness should not be confused with the state of a body under the influence of balanced forces. So, if a body is inside a liquid, the weight of which in the volume of the body is equal to the weight of the body, then the force of gravity is balanced by the buoyant force. But the body will press on the liquid (as on a support), as a result of which the stresses caused in it by the force of gravity will not disappear, but This means that it will not be in a state of weightlessness.

Let us now consider the weightlessness of bodies on artificial Earth satellites. When a satellite flies freely in orbit around the Earth, the satellite itself and all the bodies on it, in the reference system associated with the Earth’s center of mass or with the “fixed” stars, move with the same acceleration at any given moment in time. The magnitude of this acceleration is determined by the gravitational forces acting on them towards the Earth (the gravitational forces towards other cosmic bodies can be ignored, they are very small). As we have seen, this acceleration does not depend on the mass of the body. Under these conditions, there will be no interaction between the satellite and all the bodies located on it (as well as between their particles) due to gravity towards the Earth. This means that during the free flight of the satellite, all the bodies in it will be in a state of weightlessness.

The bodies not secured in the satellite ship, the astronaut himself floats freely inside the satellite; liquid poured into a vessel does not press on the bottom and walls of the vessel, so it does not flow out through the hole in the vessel; plumb lines (and pendulums) are at rest in any position in which they are stopped.

The astronaut does not need any effort to keep his arm or leg in an inclined position. His idea of ​​where is “up” and where is “down” disappears.

If you give a body speed relative to the satellite cabin, then it will move rectilinearly and uniformly until it collides with other bodies.

To eliminate possible dangerous consequences effects of the state of weightlessness on the life activity of living organisms, and above all humans, scientists are developing various ways to create artificial “gravity,” for example, by imparting rotational motion around the center of gravity to future interplanetary stations. The elastic force of the walls will create the necessary centripetal acceleration and cause deformations in the bodies in contact with them, similar topics, which they had in the conditions of the Earth.

Weight as the force with which any body acts on a surface, support or suspension. Weight arises 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 350 km from Earth. At this distance, the acceleration of gravity (g) is 8.8 m/s2, which is only 10% less than on the surface of the planet.

This is rarely seen in practice - gravitational influence always exists. Astronauts on the ISS are still affected by the Earth, but there is weightlessness there.

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

Weightlessness on Earth

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

If the elevator moves downward with acceleration, then the pressure on the elevator floor, and therefore the weight, will decrease. Moreover, if the acceleration is equal to the acceleration of gravity, that is, the elevator falls, the weight of the bodies will become zero.

Negative weight is observed if the acceleration of the elevator movement exceeds the acceleration of gravity - the bodies inside will “stick” to the ceiling of the cabin.

This effect is widely used to simulate weightlessness in astronaut training. The aircraft, equipped with a training chamber, rises to a considerable height. After which 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 people perform complex figures, like the “Nesterov loop,” to achieve weightlessness. In fact, modified production passenger aircraft, which are incapable of complex maneuvers, are used for training.

Physical Expression

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

where m is body mass,
g – free fall acceleration,
a is the acceleration of the support.

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

The introduction of inertial forces simplifies and makes more visual the solution of a number of questions and problems about the motion of bodies in non-inertial systems. Let us now obtain refined expressions for the weight of the body and the acceleration of gravity (see § 12).

The force with which a body is attracted to the Earth is called the force of gravity. The weight of the body is equal to the force with which a body motionless relative to the Earth and located in the void presses on a horizontal support or stretches a spring due to attraction to the Earth.

Thus, the weight of the body is equal to the force of gravity; therefore, we will often use these terms interchangeably.

If the Earth did not have a daily rotation, then the weight of the body would be equal to the gravitational force of the body towards the Earth, determined by formula (15). Thanks to the daily rotation of the Earth (in which all terrestrial bodies participate) a body lying on earth's surface, in addition to the gravitational force directed along the radius to the center O of the Earth, there is a centrifugal force of inertia directed along the line of continuation of the radius from the axis of rotation of the Earth (Fig. 19). Let's decompose into two components: in the direction of the radius in the direction perpendicular to the component is balanced by the force of friction of the body on the earth's surface; component

counteracts the body's gravitational force towards the Earth. Therefore, the force of attraction of a body to the Earth, i.e., the weight of the body, will be expressed by the difference between the force of gravity and the component of the centrifugal force of inertia

where is the geographic latitude of the body's location. Taking into account formulas (15) and (20), we obtain

where body mass, Earth mass, rad/s is the angular velocity of the Earth’s daily rotation. But that's why

From formula (21) it follows that the weight of a body depends on the latitude of the place: it decreases from the pole to the equator due to an increase in this direction (see § 13). At the Pole

Since the acceleration of gravity is

Consequently, the acceleration due to gravity also decreases from the pole to the equator. True, this decrease is so small (does not exceed that it is not taken into account in many practical calculations.

With the help of inertial forces one can simply explain the so-called state of weightlessness. The body subject to this condition does not exert pressure on the supports, even when in contact with them; in this case, the body does not experience deformation.

The state of weightlessness occurs when only the force of gravity acts on a body, that is, when the body moves freely in a gravitational field.

This occurs, for example, in an artificial Earth satellite launched into orbit and freely moving in the field of gravity, i.e., rotating around the Earth (see § 19).

During rotational motion, as we already know, a centrifugal force of inertia arises. Since the centrifugal force of inertia acting on each particle of the body located in the satellite (and the satellite itself) is equal in magnitude and opposite in direction to the gravitational force acting on the corresponding particle, these forces are mutually balanced. As a result, the body does not undergo deformation and does not exert pressure on the walls of the satellite (and other possible supports), i.e., it turns out to be weightless.

Bodies located in a spacecraft freely (with the engines turned off) moving along any trajectory in airless space in a gravitational field also become weightless. Of course, along with all the bodies in the ship, the astronaut also becomes weightless.

The astronaut's physiological feeling of weightlessness is expressed in the absence of the usual stresses and loads that are caused by gravity. Deformation stops internal organs, the constant voltage of the series disappears skeletal muscles, the activity of the vestibular apparatus (providing a person’s sense of balance) is disrupted, the sense of “up” and “down” disappears, and the implementation of some natural functions of the body is complicated. Such familiar actions as, for example, pouring water from a vessel also cause difficulties: the water now has to be literally shaken out of the vessel.

To eliminate these and other difficulties during a person’s long stay in space, it is proposed to create an artificial “gravity” on the space station. For this purpose, the station will be designed in the form of a large rotating disk with work areas located on its periphery. The centrifugal force of inertia arising in this case will act as the missing gravitational force.

Another important phenomenon is associated with the rotation of the Earth around its axis: the deviation of bodies moving along the Earth’s surface from their original direction. Let a body of mass moving rectilinearly in the northern hemisphere, for example along the meridian, move from the latitude of which the linear rotation speed corresponds to the latitude of which the speed corresponds (Fig. 20). By inertia, the body retains its initial rotation speed and at latitude it will have a greater rotation speed than the earth's surface beneath it. In other words, at latitude the body acquires acceleration relative to the earth's surface, directed to the right perpendicular to the movement of the body. As a result, the body will deviate to the right from the original (meridional) direction of movement and its trajectory (relative to the earth's surface) will turn out to be curvilinear.

An observer associated with the rotating Earth (and therefore not noticing its rotation) will explain this phenomenon by the action of a certain inertial force on the body, directed to the right perpendicular to the speed of movement of the body and equal in magnitude to so. This force is called the Coriolis force, or Coriolis force.

The Coriolis force acts only on moving (relative to the Earth) bodies. Being perpendicular to the speed of movement of the body, it changes only the direction, but not the magnitude of this speed; In the northern hemisphere, the Coriolis force is directed to the right, in the southern hemisphere - to the left. To avoid misunderstandings, we emphasize that the Coriolis force occurs in any (and not just in the meridional) direction of motion of bodies.

The magnitude of the Coriolis force is proportional to the speed of movement of the body, its mass and the angular velocity of the daily rotation of the Earth. Since the angular velocity of the Earth's rotation is small, the Coriolis force can take on large values ​​and cause significant deviations only in bodies moving at high speed (for example, intercontinental ballistic missiles in flight).

If the movement of bodies on the earth's surface is limited (in the lateral direction) by any connection, then the body will press on this connection with a force equal to the Coriolis force. With prolonged exposure, the Coriolis force, despite its relatively small value, causes a noticeable effect. Thanks to it, the rivers of the northern hemisphere wash away their right banks (Beer's law), and air currents acquire a right rotation (clockwise). The action of the Coriolis force also causes increased wear on the right rail of railway tracks in the northern hemisphere.

Problem 6. A load was suspended from a tendon with a length of cm and a diameter. At the same time, it lengthened to cm. Determine the modulus of elasticity of the tendon.

Solution. The tendon is subjected to unilateral tensile deformation, therefore, according to formula (12),

where is the cross-sectional area, the amount of tendon elongation.

Problem 7. Find the traction force developed by the engine of a car moving uphill with acceleration (Fig. 21). The slope of the mountain is equal for each path, the mass of the car is the coefficient of friction

Solution. Let's express the weight of the car:

Let's break it down into two components (Fig. 21): the force that rolls the car down the mountain (parallel to the surface of the mountain), and the force that presses it to the surface of the mountain, i.e. the force normal pressure(perpendicular to the surface of the mountain).

The engine of a car moving uphill must overcome the rolling force and friction force; in addition, it must provide the car with acceleration a. Therefore the traction force

According to the law of universal gravitation, all bodies are attracted to each other, and the force of attraction is directly proportional to the masses of the bodies and inversely proportional to the square of the distance between them. That is, the expression “absence of gravity” makes no sense at all. At an altitude of several hundred kilometers above the Earth's surface - where manned spacecraft and space stations fly - the Earth's gravitational force is very strong and practically no different from the gravitational force near the surface.

If it were technically possible to drop an object from a tower 300 kilometers high, it would begin to fall vertically and with the acceleration of free fall, just as it would fall from the height of a skyscraper or from the height of a person. Thus, during orbital flights, the force of gravity is not absent or weakened to a significant extent, but is compensated. Just as for watercraft and balloons, the force of gravity of the earth is compensated by the Archimedean force, and for winged aircraft - by the lifting force of the wing.

Yes, but the plane flies and does not fall, and the passenger inside the cabin does not fly like astronauts on the ISS. During a normal flight, the passenger feels his weight perfectly, and it is not the direct lifting force that keeps him from falling to the ground, but the reaction force of the support. Only during an emergency or artificially caused sharp decline does a person suddenly feel that he stops putting pressure on the support. Weightlessness arises. Why? But because if the loss of height occurs with an acceleration close to the acceleration of free fall, then the support no longer prevents the passenger from falling - she herself falls.

spaceref.com It is clear that when the plane stops sharply descending, or, unfortunately, falls to the ground, then it will become clear that gravity has not gone away. For in terrestrial and near-Earth conditions, the effect of weightlessness is possible only during a fall. Actually, a long fall is an orbital flight. To a spaceship, moving in orbit at escape velocity, is prevented from falling to Earth by the force of inertia. The interaction of gravity and inertia is called “centrifugal force,” although in reality such a force does not exist, it is in some way a fiction. The device tends to move in a straight line (tangentially to the near-Earth orbit), but the Earth's gravity constantly “spins” the trajectory of movement. Here, the equivalent of gravitational acceleration is the so-called centripetal acceleration, as a result of which it is not the value of the speed that changes, but its vector. And therefore the speed of the ship remains unchanged, but the direction of movement is constantly changing. Since both the spacecraft and the astronaut are moving at the same speed and with the same centripetal acceleration, the spacecraft cannot act as a support on which the weight of a person presses. Weight is the force of a body acting on a support that arises in the field of gravity and prevents it from falling. But a ship, like a sharply descending airplane, does not prevent it from falling.

That is why it is completely wrong to talk about the absence of Earth’s gravity or the presence of “microgravity” (as is customary in English-language sources) in orbit. On the contrary, the gravity of the earth is one of the main factors in the phenomenon of weightlessness that occurs on board.

We can talk about true microgravity only when applied to flights in interplanetary and interstellar space. Far from a large celestial body, the gravitational forces of distant stars and planets will be so weak that the effect of weightlessness will arise. We have read more than once in science fiction novels about how to deal with this. Space stations in the form of a torus (wheel) will spin around a central axis and create an imitation of gravity using centrifugal force. True, in order to create the equivalent of gravity, you will have to give the torus a diameter of more than 200 m. There are other problems associated with artificial gravity. So all this is a matter of the distant future.

Today, perhaps, even small child. Such widespread This fact was served by numerous science fiction films about Space. However, in reality, few people know why there is weightlessness in Space, and today we will try to explain this phenomenon.

False Hypotheses

Most people, having heard the question about the origin of weightlessness, will easily answer it by saying that such a state is experienced in Space for the reason that the force of gravity does not act on bodies there. And this will be a completely wrong answer, since the force of gravity acts in Space, and it is this force that holds all cosmic bodies in their places, including the Earth and the Moon, Mars and Venus, which inevitably revolve around our natural luminary - the Sun.

Having heard that the answer is incorrect, people will probably pull out another trump card from their sleeves - the absence of an atmosphere, the complete vacuum observed in Space. However, this answer will not be correct either.

Why is there weightlessness in space?

The fact is that the weightlessness that astronauts on the ISS experience arises due to a whole combination of various factors.

The reason for this is that the ISS orbits the Earth at a tremendous speed exceeding 28 thousand kilometers per hour. This speed affects the fact that the astronauts on the station cease to feel Earth’s gravity, and a feeling of weightlessness is created relative to the ship. All this leads to the fact that the astronauts begin to move around the station exactly as we see in science fiction films.

How to simulate weightlessness on Earth

Interestingly, the state of weightlessness can be artificially recreated within Earth's atmosphere, which, by the way, is what specialists from NASA are successfully doing.

NASA has such an aircraft on its balance sheet as the Vomit Comet. This is a completely ordinary airplane, which is used to train astronauts. It is he who is able to recreate the conditions of being in a state of weightlessness.

The process of recreating such conditions is as follows:

1. The airplane sharply gains altitude, moving along a pre-planned parabolic trajectory.
2. Reaching the top point of the conventional parabola, the airplane begins a sharp downward movement.
3. Due to a sharp change in the trajectory of movement, as well as the flight of the aircraft downward, all people on board begin to experience conditions of weightlessness.
4. Having reached a certain point of descent, the airplane levels its trajectory and repeats the flight procedure, or lands on the surface of the Earth.