Balance

We explain what balance is in physics and its three different states. Also, the sense of balance and other uses of the term.

What is balance?

When we talk about balance, in general, we refer to the state of a body in which the forces acting on it cancel each other or cancel each other out, allowing it to remain in the same place or the same form, without moving or modifying.

This is an idea that we usually represent through the scale, that tool we use to weigh objects. So much so, that the word itself comes from Latin equilibriummade up of aequus“equal”, and pound“balance.”

Scales work by placing the object to be weighed on one side and placing certain counterweights whose weight is known on the other, until both sides reach the same level, that is, until the scale does not tilt in any direction. This point is the point of balance, and any body or object in reality can experience it, as long as the forces acting on it cancel each other, leaving it at rest.

There are, in this way, three different types of equilibrium states recognized by physics, in which an object or a body can find itself:

• Stable balancewhen the body or object resumes its position of stability once the forces acting on it have ceased, thus demonstrating a marked tendency towards balance. For example, a pendulum that we push with our hand will move for a while, until the effect of gravity always stops it at the same exact point of rest.
• Unstable balancewhen the body or object maintains a position of rest only as long as a certain force acts on it that compensates for the others, so that, when said force ceases, the object loses its balance and moves to other places. For example, a pencil that we hold on its tip will fall in different directions when we release it, since its resting point depends on the strength of our hand.
• Indifferent balancewhen the body or object is capable of losing its rest position and reaching a new one spontaneously, without the need for new forces to act on it. This is what happens, for example, when we leave a ball on a completely flat surface: it will not move in any direction, and if we push it a little, it will change location but will immediately regain its balance.

Sense of balance

We say we have balance when we are able to move and carry out actions while standing uprightstanding, although often in those cases we tend to move our arms, precisely, like the plates of the scale, to keep the body in its center of gravity.

Equilibriumception is the perception of the balance of the body. It is a physiological sense that we share with animals, whose function is to guide our body and prevent us from falling.

Thanks to it we can walk along a narrow railing and remain standing, or birds can perform pirouettes in the air and recover their flying position, or even beings as primitive as jellyfish can return to their “face up” position when they hit the ground. the return All of these are ways to maintain balance.

In the case of humans and other mammals, This sense depends on the internal structures of the ear. It can be affected by illnesses or infections that trigger dizziness, disorientation and nausea.

These same sensations can be provoked when someone is on objects in constant motion, such as boats, airplanes or roller coaster cars. Even astronauts have reported similar dizziness, as a result of prolonged exposure to weightlessness.

There are two different types of this body balance:

• Static balancewhen it refers to the ability to remain still and upright, without falling, on our feet or on one alone, or on an object, etc.
• Dynamic balancewhen it refers to the ability to stay upright and stable while doing other types of physical activities, such as walking on a tightrope or juggling on it, for example.

Other uses of the term balance

In addition to those detailed so far, the word balance has other much more specific uses within certain fields of knowledge or disciplines, such as the following:

• Chemical balance. Term used in chemistry to indicate that a reversible chemical reaction reaches a stable state, that is, when substances move between chemicals at the same rate, without producing a net change of any kind.
• Thermal balance. Term from the field of physics, which refers to the state of two bodies in direct contact, whose initially different temperatures end up becoming equal, as the heat radiates in the direction from the hottest to the least hot, altering the temperature of both bodies.
• Ecological balance. Also called balance of nature, it is a concept that proposes the state of balance or homeostasis of biological systems, within which there is a tendency to preserve order: so many predators for so many prey, preying and reproducing at a fixed rate and ordered. A small modification within the system is corrected by negative feedback from it. On the other hand, large and abrupt changes break the balance and plunge the ecological system into chaos.
• Economic balance. This is the name given to the point in any productive economic system in which the demand for goods is identical to the supply, thus allowing prices to remain stable and in balance, without the need for forces external to the productive circuit to intervene.

Continue with: Inertia

References

• “Balance” in the Dictionary of the language of the Royal Spanish Academy.
• “Types of balance” in PROED Virtual Classrooms (Argentina).
• “Balance and its importance in physical activity” at Pontificia Universidad Católica del Perú.
• “Balance” in the Xunta de Galicia (Spain).
• “Equilibrioception” on Wikipedia.
• “Chemical balance” on Wikipedia.
• “Economic equilibrium” on Wikipedia.
• “Ecological balance” in Wikipedia.
• “Thermal balance” in Wikipedia.