In aviation and space medicine, overload is considered an indicator of the magnitude of acceleration affecting a person when moving. It represents the ratio of the resultant moving forces to the mass of the human body.

Overload is measured in units of multiple body weight under terrestrial conditions. For a person located on the earth's surface, the overload is equal to one. The human body is adapted to it, so it is invisible to people.

If an external force imparts an acceleration of 5 g to any body, then the overload will be equal to 5. This means that the weight of the body under these conditions has increased five times compared to the original one.

When a conventional airliner takes off, passengers in the cabin experience a g-force of 1.5 g. According to international standards, the maximum permissible overload value for civil aircraft is 2.5 g.

At the moment the parachute opens, a person is exposed to inertial forces that cause an overload reaching 4 g. In this case, the overload indicator depends on the airspeed. For military parachutists, it can range from 4.3 g at a speed of 195 kilometers per hour to 6.8 g at a speed of 275 kilometers per hour.

The reaction to overloads depends on their magnitude, the rate of increase and the initial state of the body. Therefore, both minor functional changes (a feeling of heaviness in the body, difficulty moving, etc.) and very serious conditions can occur. These include complete loss of vision, dysfunction of the cardiovascular, respiratory and nervous systems, as well as loss of consciousness and the occurrence of pronounced morphological changes in tissues.

In order to increase the resistance of the pilots' body to acceleration in flight, anti-g and altitude-compensating suits are used, which, during overloads, create pressure on the abdominal wall and lower extremities, which leads to a delay in the outflow of blood to the lower half of the body and improves blood supply to the brain.

To increase resistance to acceleration, training is carried out in a centrifuge, hardening the body, and breathing oxygen under high pressure.

When ejecting, rough landing of an airplane or landing by parachute, significant overloads occur, which can also cause organic changes in the internal organs and spine. To increase resistance to them, special chairs are used that have in-depth headrests and secure the body with belts that limit the displacement of the limbs.

Overload is also a manifestation of gravity on board a spacecraft. If under terrestrial conditions the characteristic of gravity is the acceleration of free fall of bodies, then on board a spacecraft the characteristics of overload also include the acceleration of gravity, equal in magnitude to the reactive acceleration in the opposite direction. The ratio of this quantity to magnitude is called the "overload factor" or "overload".

In the acceleration section of the launch vehicle, the overload is determined by the resultant of non-gravitational forces - the thrust force and the aerodynamic drag force, which consists of the drag force directed opposite to the speed and the lift force perpendicular to it. This resultant creates non-gravitational acceleration, which determines the overload.

Its coefficient in the acceleration section is several units.

If a space rocket, under Earth conditions, moves with acceleration under the influence of engines or experiencing environmental resistance, then the pressure on the support will increase, causing an overload. If the movement occurs with the engines turned off in a vacuum, then the pressure on the support will disappear and a state of weightlessness will occur.

When a spacecraft is launched, the astronaut's magnitude varies from 1 to 7 g. According to statistics, astronauts rarely experience overloads exceeding 4 g.

The ability to withstand overloads depends on the ambient temperature, the oxygen content in the inhaled air, the length of time the astronaut spent in weightlessness before acceleration, etc. There are other more complex or less subtle factors whose influence is not yet fully understood.

Under the influence of acceleration exceeding 1 g, an astronaut may experience visual impairment. Acceleration of 3 g in the vertical direction that lasts more than three seconds can cause severe impairment of peripheral vision. Therefore, it is necessary to increase the level of illumination in the compartments of the spacecraft.

During longitudinal acceleration, the astronaut experiences visual illusions. It seems to him that the object he is looking at is moving in the direction of the resulting vector of acceleration and gravity. With angular accelerations, an apparent movement of the object of vision occurs in the plane of rotation. This illusion is called circumgyral and is a consequence of the effects of overload on the organs of the inner ear.

Numerous experimental studies, which were started by the scientist Konstantin Tsiolkovsky, have shown that the physiological effects of overload depend not only on its duration, but also on the position of the body. When a person is in an upright position, a significant part of the blood shifts to the lower half of the body, which leads to a disruption in the blood supply to the brain. Due to the increase in their weight, the internal organs move downwards and cause severe tension on the ligaments.

To weaken the effect of high accelerations, the astronaut is placed in the spacecraft in such a way that the overloads are directed along the horizontal axis, from the back to the chest. This position ensures effective blood supply to the astronaut’s brain at accelerations of up to 10 g, and for a short time even up to 25 g.

When a spacecraft returns to Earth, when it enters the dense layers of the atmosphere, the astronaut experiences braking overloads, that is, negative acceleration. In terms of integral value, braking corresponds to acceleration at start.

A spacecraft entering the dense layers of the atmosphere is oriented so that the braking overloads have a horizontal direction. Thus, their impact on the astronaut is minimized, as during the launch of the spacecraft.

The material was prepared based on information from RIA Novosti and open sources

Received a personal message:

Message from kkarai
>> There was an overload, Yuri. And everyone is waiting for an overload. Well, let’s look at the combat application (all smokers want to know about the overload, how much it weighs, how much it hurts).

I sat down to write a response. But then I thought that perhaps it would be interesting to other non-pilot readers interested in aviation.
It never hurts from aerobatics (overload). They try to do it painfully when they begin to take dirty and petty revenge on you for your work, for some story of yours that some petty soul did not like, scum who with gusto collects gossip about what could have happened or did not happen at all, but He tells with the air of an expert what allegedly happened. Unfortunately, there were too many of these from the Borisoglebsk School... But the wrong one was attacked!
What about overload? Why would there be pain? Overload is a coefficient that shows how many times your body weight exceeds what it is in normal condition. It can be represented as a formula like this:

G real. = G normal n y

Where G is weight, and n y is vertical overload (head-pelvis).
From the formula it is clear that you are currently subject to an overload equal to one. If n y is zero, this is weightlessness. If you stand on your hands against the wall and the weight is directed from the pelvis to the head, you will feel a negative overload (minus one).
And in flight there are also lateral overloads n z (I don’t decipher them, they are insignificant), longitudinal g-forces n x (chest - back) - these are very pleasant accelerations, on takeoff, for example (positive, this is acceleration), when releasing the braking parachute (negative, this is braking) .
Vertical overloads are the worst tolerated; they also most often affect the pilot in flight. On a deep turn, the overload should be kept at 3-6-8 units. And the greater the roll, the greater the overload required to keep the plane on the horizon and the smaller the turning radius will be. The overload will be greater than necessary for a given roll - the fighter will climb; if less, the turn will turn with a “burrow” (i.e., with the nose lowered, the altitude will begin to fall; in order to correct the deep “burrow” you will have to pull out of the roll, and this will air combat is dangerous, especially if the enemy is already behind and taking aim). And the greater the overload on a bend, the greater the thrust the engine must have, otherwise the speed will begin to drop and you will have to reduce the overload; But if you reduce the overload, you won’t knock down the enemy or you’ll be shot down.
When performing a Nesterov loop or half-loop, when “twisting” the plane in the first part of the figure, n y reaches 4.5-6 units. Those. the pilot's weight increases 4.5-6 times: if the pilot weighs 70 kg, then when performing aerobatics in this figure his weight will be 315-420 kg. At these times, the weight of the arms, legs, head, blood, and finally, increases! It is impossible to perform this figure with less overload - the trajectory will become stretched and the plane will lose speed at the top of the loop, which can lead to a spin. It’s also not possible with a larger one (well, depending on the type of aircraft) - the plane will reach supercritical angles of attack and will also lose speed. Therefore, the overload must be optimal (it’s different for each type of aircraft). In the upper part of the Nesterov loop, the pilot does not hang on the belts, but is also pressed against the seat, because the plane must be “twisted” with an overload of 2-2.5. The lower part of the loop is performed with an overload of 3.5-4.5 (depending on the type).
The maximum overloads that the human body can withstand are from (+)12 to (-)4.
The danger of large vertical overloads is that blood flows away from the brain. If a pilot is relaxed during aerobatics and does not tense his body muscles, he may lose consciousness. The pilot’s field of vision narrows (darkness falls on all sides, like a diaphragm in a lens), if the overload is not “allowed”, the person will pass out. Therefore, during aerobatics, the pilot strains all the main muscle groups. Therefore, you need to maintain your physical condition in good shape.

The first photo shows what the cadet sees in front of him before creating a large overload. On the second: a large overload was created, the pilot did not have time to strongly strain the muscles of the whole body, the blood drained from the brain, a veil surrounded the vision from all sides, a little more the instructor would pull the handle towards himself and the cadet would lose consciousness...

The principle of operation of the anti-g suit (APS) is based on these same factors; its chambers compress the pilot’s body on the stomach, thighs and calves, preventing the outflow of blood. A special machine supplies air to the PPK chambers depending on the overload: the greater the overload, the greater the compression of the pilot’s body. But! It must be borne in mind that the PPK does not relieve overload, but only makes it easier to bear!
The presence of a PPK significantly increases the fighter's capabilities. And in an air battle, a pilot with a PPK gets an advantage over an enemy who “forgot” to put it on!

The PPC does not work under negative g-loads, when, on the contrary, blood rushes to the brain in a large flow. But with negative overloads (when you hang on the harness, your head rests against the glazing of the cockpit canopy, and dust from a poorly cleaned floor gets into your face and eyes), air battles are not carried out. I know only one pilot who could escape from an enemy attack with a negative overload, shoot accurately and shoot down planes from any position of his fighter, incl. inverted - Chief Lieutenant Erich Hartmann. During the war, he made 1,404 combat missions, in 802 air battles he scored 352 aerial victories, 344 of them over Soviet aircraft. We can only talk about 802 air battles conditionally. E. Hartman, as a rule, attacked the enemy from the direction of the sun and left, and when an air battle was forced on him, he was shot down 11 times by less famous Soviet fighters - he was bailed out or made an emergency landing. But with this ability (to hit a target from any position) he surprised his instructor pilots even while still a cadet, studying at the Ts-Flyugshull (a flight school that prepared for the production of fighters).
Doctors recommend that if fatigue occurs during a flight, manually create pressure in the PPK chambers by pressing the button of the machine, which supplies air to the suit. Squeezing the whole body is an effect on the acupuncture of the nervous system, somewhere and in the right place there will be an effect. I have used this method many times myself! I squeezed myself - after 3-5 seconds the air was released, then again. And so 3-4 times. And like a cucumber! The aviation medics are right! Fatigue relieves as if by hand! And your mood and performance improve!

At aviation festivals you can see virtuosos performing “reverse” aerobatics - performing turns, dives and slides, Nesterov loops, half-loops, combat turns and inverted coups. (That is, with negative overload.) And their body remains in such tension for 5-7 minutes! This is truly skill! Supreme craftsmanship!! How they manage to do this is hard for me to figure out! It takes years of training. This skill increases hundreds of times when such aerobatics is performed in pairs: one pilot pilots the plane normally, and the other ten meters above him stands in an inverted position (cockpit to cockpit) and thus maintains his place in the ranks! The slightest inconsistency in actions and a collision is inevitable, both will die! However, such aerobatics will be elongated in the vertical plane - this is so as not to exceed the negative overload for an inverted plane (-) 4. After landing, these pilots who performed reverse aerobatics most often have red whites of their eyes (if the negative overload is extreme, and then small capillaries burst ). But only sports aircraft fly this way; combat aircraft can fly in an inverted position for no more than 30 seconds (to provide fuel to the engines from negative G tanks). These are truly high-quality pilot athletes! I've never flown like this! Or rather, it happened once: I got away from a fighter that was attacking me in a training air battle by pushing the handle away from me on a turn (it turned out to be a “reverse” turn) Gone! The “enemy” (regiment commander Lieutenant Colonel Boris Tikhonovich Tunenko, who had experience of real air battles in the Middle East, where he opened the account with one F-4e “Phantom” shot down) was not ready for such a maneuver and did not follow me. They lost sight of me, I attacked him from the rear hemisphere - from above and “knocked down” him. But it happened once, and I will say that the feeling was not pleasant! And I was convinced: this technique of E. Hartman is very effective, primarily due to the unexpectedness of its application. (However, no, I had another such case, when I was “pinched” by two fighters in a training air battle, and I got away from them using a similar method. But I’ll tell you about this some other time.)
And to the sports pilots who can fly like this regularly, I take my hat off!
In modern close air combat, the overload should be 6-8 units. and more throughout the entire battle! If it’s less, you won’t get shot down, they’ll shoot you down!
During ejection, the vertical overload impact on the pilot’s body reaches 18-20 units. Not much pleasant.
“But how can that be! - you exclaim. - You just said that the limit for the human body is (+)12! And here are 20 units!”
That's right! I don't refuse! It’s just that when a catapult is fired, the effect of overload on the pilot’s body is short-lived, a fraction of a second. Therefore, with the correct position of the pilot’s body (the head is straight and forcefully pressed into the headrest of the seat, the back is pressed against the back of the seat, the hips and torso form a right angle, and the spine, in a vertical position, forms a perpendicular to the seat; in addition, all the muscles of the body must be very tense) negative aspects are minimized and the vertebrae do not have time to spill out into their underpants! If at the moment of the shot the head is tilted forward and down, to the side, or even simply not pressed forcefully against the headrest (due to the enormous overload, it will tilt itself), if the pilot fell apart in the cockpit before ejection, as if at home in his favorite chair in front of the TV, a fracture of the cervical vertebrae in the first case and the lumbar spine in the second cannot be avoided. And the sooner rescuers find such a pilot, the better. He won't survive on his own! Then he will lie on boards in plaster from head to toe for 6 to 12 months, like a log, without turning over. The spine will consolidate, of course, but it will no longer be the one created by nature. And the higher the fracture was, the more organs in his body will work worse and worse. Such people reduce their life by 12-20 years! Once in the Kiev hospital, when I was undergoing a commission, I met Alexander Sanatov, with whom I served in Mongolia. Many years ago, Sasha, as a lieutenant, was forced to eject at the limit with an incorrect position in his seat! (“Ah! It’ll do!”) As a result, he suffered a fracture of the lumbar spine. Long persistent months and years of treatment. I ask: “How is it now?” - “I live on medications... 7-8 months a year in the hospital!..” (Someday I will describe this case... It is interesting and instructive in its own way...)
I heard that on some of the first American planes the pilots were ejected to the side. But there was a complex system for destroying the side wall of the cabin, and it was not always possible to preserve the pilots’ cervical vertebrae. This was abandoned. There were planes where crew members (navigator, gunner) ejected down. (In the first series of Tu-16, all crew members, except for the pilots who ejected upward, were also on the Tu-22.) But in this case, the minimum rescue altitudes sharply increased (and sometimes made it impossible), and such pilots went through a long period of rehabilitation...
The most optimal thing for the pilots’ health would be to eject forward. There would most likely never have been any injuries here! But technically this is simply impossible!

Overload is the ratio of the resultant of all forces (except weight) acting on the aircraft to the weight of the aircraft.

Overloads are defined in the associated coordinate system:

nx- longitudinal overload; nу- normal overload; nz- lateral overload.

Full overload is determined by the formula

Longitudinal overload nх occurs when engine thrust and drag change.

If the engine thrust is greater than the drag, then the overload is positive. If the amount of drag is greater than the engine thrust, then the overload is negative.

Longitudinal overload is determined by the formula

Lateral overload nz occurs when the aircraft is flying in a sliding state. But in terms of magnitude, the lateral aerodynamic force Z is very small. Therefore, in calculations, the lateral overload is taken equal to zero. Lateral overload is determined by the formula

The performance of aerobatic maneuvers is mainly accompanied by the occurrence of large normal overloads.

Normal overload nу is called the ratio of lift to the weight of the aircraft and is determined by the formula

Normal overload, as can be seen from formula (11.5), is created by lift. In horizontal flight in a calm atmosphere, the lift force is equal to the weight of the aircraft, therefore, the overload will be equal to unity:

Rice. 6 The effect of centrifugal inertial force on the pilot a - with a sharp increase in the angle of attack, b - with a sharp decrease in the angle of attack

In curved flight, when the lift force becomes greater than the weight of the aircraft, the overload will be greater than one.

When an airplane moves along a curved path, the centripetal force is, as already mentioned, lift, i.e., air pressure on the wings. In this case, the magnitude of the centripetal force is always accompanied by an equal, but opposite in direction, centrifugal force of inertia, which is expressed by the force of pressure of the wings on the air. Moreover, the centrifugal force acts like weight (mass), and since it is always equal to the centripetal force, when the latter increases, it increases by the same amount. Thus, aerodynamic overload is similar to an increase in the weight of the aircraft (pilot).

When overload occurs, the pilot feels as if his body has become heavier.

Normal overload is divided into positive and negative. When the overload presses the pilot into the seat, then this overload positive, if he separates him from the seat and holds him on the seat belts - negative (Fig. 6).

In the first case, the blood will flow from the head to the feet, in the second case, it will flow to the head.

As already mentioned, an increase in lift in curvilinear motion is equivalent to an increase in the weight of the aircraft by the same amount, then

(11.6)

(11.7)

Where n level - available overload.

From formula (11.7) it is clear that the amount of available overload is determined by the reserve of lift coefficients (margin of angles of attack) from those required for horizontal flight to its safe value (Su TR or Su CR).

The maximum possible normal overload can be obtained when, in flight at a given speed and flight altitude, the aircraft's ability to create lift is fully utilized. This overload can be obtained in the case when the aircraft is sharply (without a noticeable decrease in flight speed) brought to C y = C y max:

(11.8)

However, it is undesirable to bring the aircraft to such an overload, as there will be a loss of stability and a stall into a tailspin or spin rotation. For this reason, it is not recommended to sharply tilt the control stick toward you at high flight speeds, especially when exiting a dive. Therefore, the maximum possible or available overload is taken to be smaller in value in order to prevent the aircraft from entering the shaking mode. The formula for determining this overload has the form

(11.9)

For the Yak-52 and Yak-55 aircraft, graphical dependences of available overloads on flight speed are shown in Fig. 7, Fig. 8. When performing flights on Yak-52 and Yak-55 aircraft, the available normal overload is mainly limited by the strength characteristics of the aircraft.

Maximum permissible operational overload for the Yak-52 aircraft:

with wheeled chassis:

positive +7;

negative -5;

with ski chassis:

positive +5;

negative -3.

Maximum permissible operational overload for the Yak-55 aircraft:

in the training version:

positive +9;

negative -6;

in distillation version:

positive +5;

negative -3.

Exceeding these overloads in flight is prohibited, since residual deformations may appear in the aircraft structure.

When performing steady-state curved maneuvers, the overload depends on the thrust reserve of the power plant. The thrust reserve is determined from the condition of maintaining a given speed throughout the entire maneuver.

Maximum overload for available thrust PR is called the greatest overload at which the thrust of the power plant still balances the drag. It is determined by the formula

(11.10)

The maximum overload for the available thrust depends on the speed and altitude of the flight, since the above factors affect the available thrust Рр and the aerodynamic quality K on the speed. To calculate the dependence of n at PREV it is necessary to have curves Рр (V) for different altitudes and a grid of polars.

For each speed value, the values ​​of the available thrust are taken from the curve Pp (V), the value of the coefficient Cy is determined from the polar for the corresponding speed V, and calculated using formula (11.10).

When maneuvering in a horizontal plane with an overload less than available, but more than the maximum thrust, the aircraft will lose speed or flight altitude.

The force applied to a body is measured in SI units in newtons (1 N = 1 kg m/s 2). In technical disciplines, the kilogram-force is often traditionally used as a unit of measurement of force (1 kgf, 1 kg) and similar units: gram-force (1 gs, 1 G), ton-force (1 ts, 1 T). 1 kilogram-force is defined as the force exerted on a body of mass 1 kg normal acceleration, equal by definition to 9.80665 m/s 2(this acceleration is approximately equal to the acceleration of gravity). Thus, according to Newton's second law, 1 kgf = 1 kg· 9.80665 m/s 2 = 9,80665 N. We can also say that a body of mass 1 kg, resting on a support, has a weight of 1 kgf Often, for the sake of brevity, kilogram-force is simply called “kilogram” (and ton-force, respectively, “ton”), which sometimes creates confusion among people who are not accustomed to using different units.

Russian rocket science terminology traditionally uses “kilograms” and “tons” (more precisely, kilogram-force and ton-force) as units of thrust for rocket engines. Thus, when they talk about a rocket engine with a thrust of 100 tons, they mean that this engine develops a thrust of 10 5 kg· 9.80665 m/s 2$\approx$ 10 6 N.

Common mistake

Confusing newtons and kilogram-force, some believe that a force of 1 kilogram-force imparts an acceleration of 1 to a body weighing 1 kilogram. m/s 2, i.e. they write the erroneous “equality” 1 kgf / 1 kg = 1 m/s 2. At the same time, it is obvious that in fact 1 kgf / 1 kg = 9,80665 N / 1 kg = 9,80665 m/s 2- thus, an error of almost 10 times is allowed.

Example

<…>Accordingly, the force that presses on particles within the weighted average radius will be equal to: 0.74 G/mm 2 · 0.00024 = 0.00018 G/mm 2 or 0.18 mG/mm 2 . Accordingly, a force of 0.0018 mG will press on an average particle with a cross section of 0.01 mm 2.
This force will give the particle an acceleration equal to its ratio to the mass of the middle particle: 0.0018 mG / 0.0014 mG = 1.3 m/sec 2. <…>

(Emphasis apollofacts.) Of course, a force of 0.0018 milligram-force would give a particle with a mass of 0.0014 milligram an acceleration almost 10 times greater than what Mukhin calculated: 0.0018 milligram-force / 0.0014 milligram = 0.0018 mg· 9.81 m/s 2 / 0.0014 mg $\approx$ 13 m/s 2 . (It can be noted that with the correction of this error alone, the depth of the crater calculated by Mukhin, which supposedly should have formed under the lunar module during landing, will immediately drop from 1.9 m, which Mukhin requires, up to 20 cm; however, the rest of the calculation is so absurd that this amendment cannot correct it).

Body weight

A-priory, body weight is the force with which the body presses on a support or suspension. The weight of a body resting on a support or suspension (that is, stationary relative to the Earth or other celestial body) is equal to

(1)

\begin(align) \mathbf(W) = m \cdot \mathbf(g), \end(align)

where $\mathbf(W)$ is the weight of the body, $m$ is the mass of the body, $\mathbf(g)$ is the acceleration of gravity at a given point. On the Earth's surface, the acceleration due to gravity is close to the normal acceleration (often rounded to 9.81 m/s 2). Body of mass 1 kg has weight $\approx$ 1 kg· 9.81 m/s 2$\approx$ 1 kgf. On the surface of the Moon, the acceleration due to gravity is approximately 6 times less than at the surface of the Earth (more precisely, close to 1.62 m/s 2). Thus, bodies on the Moon are approximately 6 times lighter than on Earth.

Common mistake

They confuse body weight and mass. The mass of a body does not depend on the celestial body, it is constant (if we neglect relativistic effects) and is always equal to the same value - both on the Earth, and on the Moon, and in weightlessness

Example

Example

In the newspaper “Duel”, No. 20, 2002, the author describes the suffering that astronauts of the lunar module must experience when landing on the Moon, and insists on the impossibility of such a landing:

Astronauts<…>experience prolonged overload, the maximum value of which is 5. The overload is directed along the spine (the most dangerous overload). Ask military pilots if you can stand on a plane for 8 minutes. at a fivefold overload and even control it. Imagine that after three days in the water (three days of a zero-gravity flight to the Moon), you got out onto land, you were placed in the Lunar cabin, and your weight became 400 kg (g-force 5), your overalls were 140 kg, and your backpack behind the back - 250 kg. To prevent you from falling, you are held with a cable attached to your belt for 8 minutes, and then for another 1.5 minutes. (no chairs, no beds). Do not bend your legs, lean on the armrests (hands should be on the controls). Has the blood drained from your head? Are your eyes almost blind? Don't die or faint<…>
It’s really bad to force cosmonauts to control the landing in a “standing” position with a long-term 5-fold overload - it’s simply IMPOSSIBLE.

However, as has already been shown, at the beginning of the descent the astronauts experienced an overload of $\approx$ 0.66 g - that is, noticeably less than their normal earthly weight (and they did not have any backpack on their back - they were directly connected to the life support system of the ship) . Before landing, the thrust from the engine nearly balanced the weight of the craft on the Moon, so the associated acceleration is $\approx$ 1/6 g - so throughout the landing they experienced less stress than if they were simply standing on the ground. In fact, one of the tasks of the described cable system was precisely to help astronauts stay on their feet in conditions of low weight.

In this article, a physics and mathematics tutor talks about how to calculate the overload experienced by the body during acceleration or braking. This material is very poorly covered in school, so students very often do not know how to implement overload calculation, but the corresponding tasks are found on the Unified State Exam and the Unified State Exam in physics. So read this article to the end or watch the attached video tutorial. The knowledge you gain will be useful to you in the exam.

Let's start with definitions. Overload is the ratio of the weight of a body to the magnitude of the force of gravity acting on this body at the surface of the earth. Body weight- this is the force that acts from the body on the support or suspension. Please note that weight is exactly strength! Therefore, weight is measured in newtons, and not in kilograms, as some believe.

Thus, the overload is a dimensionless quantity (newtons divided by newtons, resulting in nothing left). However, sometimes this quantity is expressed in terms of acceleration due to gravity. They say, for example, that the overload is equal to , meaning that the weight of the body is twice the force of gravity.

Overload calculation examples

We will show how to calculate overload using specific examples. Let's start with the simplest examples and move on to more complex ones.

Obviously, a person standing on the ground does not experience any overload. Therefore, I would like to say that its overload is zero. But let's not make hasty conclusions. Let's draw the forces acting on this person:

Two forces are applied to a person: the force of gravity, which attracts the body to the ground, and the reaction force counteracting it from the side of the earth's surface, directed upward. In fact, to be precise, this force is applied to the soles of a person's feet. But in this particular case, this does not matter, so it can be postponed from any point on the body. In the figure it is plotted away from the human center of mass.

The weight of a person is applied to the support (to the surface of the earth), in response, in accordance with Newton’s 3rd law, an equal in magnitude and oppositely directed force acts on the person from the side of the support. This means that to find the weight of the body, we need to find the magnitude of the ground reaction force.

Since a person stands still and does not fall through the ground, the forces that act on him are compensated. That is, and, accordingly, . That is, the calculation of overload in this case gives the following result:

Remember this! In the absence of overloads, the overload is 1, not 0. No matter how strange it may sound.

Let us now determine what the overload of a person who is in free fall is equal to.

If a person is in a state of free fall, then only the force of gravity acts on him, which is not balanced by anything. There is no ground reaction force, and there is no body weight. A person is in a so-called state of weightlessness. In this case, the overload is 0.

The astronauts are in a horizontal position in the rocket during its launch. This is the only way they can withstand the overload they experience without losing consciousness. Let's depict this in the figure:

In this state, two forces act on them: the ground reaction force and the force of gravity. As in the previous example, the weight modulus of the astronauts is equal to the magnitude of the support reaction force: . The difference will be that the support reaction force is no longer equal to the force of gravity, as last time, since the rocket is moving upward with acceleration. With the same acceleration, the astronauts also accelerate synchronously with the rocket.

Then, in accordance with Newton’s 2nd law in projection onto the Y axis (see figure), we obtain the following expression: , whence . That is, the required overload is equal to:

It must be said that this is not the greatest overload that astronauts have to experience during a rocket launch. The overload can reach up to 7. Prolonged exposure to such overloads on the human body inevitably leads to death.

At the bottom point of the “dead loop”, two forces will act on the pilot: downward - force , upward, to the center of the “deaf loop” - force (from the side of the seat in which the pilot is sitting):

The pilot’s centripetal acceleration will also be directed there, where km/h m/s is the speed of the aircraft and is the radius of the “loop”. Then again, in accordance with Newton’s 2nd law, in projection onto an axis directed vertically upward, we obtain the following equation:

Then the weight is . So, the overload calculation gives the following result:

A very significant overload. The only thing that saves the pilot’s life is that it doesn’t last very long.

And finally, let’s calculate the overload experienced by the car driver during acceleration.

So, the final speed of the car is km/h m/s. If a car accelerates to this speed from rest in c, then its acceleration is equal to m/s 2. The car is moving horizontally, therefore, the vertical component of the ground reaction force is balanced by the force of gravity, that is. In the horizontal direction, the driver accelerates along with the car. Therefore, according to Newton’s 2-law, in projection onto the axis co-directed with the acceleration, the horizontal component of the support reaction force is equal to .

We find the magnitude of the total support reaction force using the Pythagorean theorem: . It will be equal to the weight modulus. That is, the required overload will be equal to:

Today we learned how to calculate overload. Remember this material, it can be useful when solving tasks from the Unified State Exam or Unified State Exam in physics, as well as in various entrance exams and olympiads.

Material prepared by Sergey Valerievich