What is a force?

What Does Force Mean

We explain what a force is for physics, its characteristics and its types according to each theory. Also, how it is measured and various examples.

For a movement to start or stop a force is necessary.

What is a force?

In technical terms, a force is such a magnitude that change the amount of movement or the shape given to a body or particle . It should not be confused with the concepts of effort or energy .

Commonly, the concept of force is explained in the terms of classical mechanics established by the principles of Isaac Newton (1642-1727), known as the Laws of Motion and published in 1687 in his Principia Mathematica . According to classical mechanics, the force that affects a body is responsible for changes in its state of motion, such as its rectilinear path and uniform displacement , and for giving it an acceleration (or deceleration). Furthermore, any force acting on a body generates an identical force, but in the opposite direction. We normally speak of force in our daily lives, without necessarily using this word as physics does . The force is studied by physics and according to it , four fundamental forces are recognized at the quantum level : the gravitational force, the electromagnetic force, the strong nuclear force and the weak nuclear force.

In contrast, in Newtonian (or classical) mechanics, there are many other identifiable forces , such as friction force, gravitational force, centripetal force, etc. See also: Power in physics

Force characteristics

A force can be thought of as a physical entity that describes the intensity of interactions between objects , closely related to energy .

For classical mechanics, every force is composed of a magnitude and a direction , which is why it is denoted by a vector . This means that it is a vector quantity, not a scalar one.

Types of force

According to Einstein, massive objects bend space-time.

There are several types of force, depending on their nature and focus: According to Newtonian mechanics:

  • Force friction . It is the force that opposes the change of movement of the bodies, exerting a resistance to leave the state of rest, or of movement, as we can perceive it when starting a heavy object when pushing it.
  • Gravitational force. It is the force exerted by the mass of bodies on nearby objects, attracting them towards each other. This force becomes noticeable when all or some of the interacting objects are very massive. The example par excellence is the planet Earth and the objects and beings that we live on its surface; there is a gravitational attractive force between them.
  • Electromagnetic force It is the attractive and repulsive force that is generated by the interaction of electromagnetic fields.

You can also talk about:

  • Contact force. It is the force that is exerted from direct physical contact between one body and another.
  • Force at a distance. It is the force that can be exerted without any physical contact between the bodies.

According to relativistic or Einsteinian mechanics:

  • Gravitational force. It is the force that seems to exist when massive objects curve space - time around them, forcing smaller objects to deviate their trajectories and approach them.
  • Electromagnetic force It is the force exerted by electromagnetic fields on the charged particles of matter , following the expression of the Lorenz force.

According to quantum mechanics:

  • Gravitational force. It is the force exerted by one masses on the other, being a weak force, in one direction only (attractive), but effective over long distances.
  • Force electromagnetic . It is the force that affects electrically charged particles and the electromagnetic fields that they generate, being the force that allows molecular bonding. It is stronger than gravitational and has two senses (attraction-repulsion).
  • Strong nuclear force. It is the force that keeps the nuclei of atoms stable, keeping neutrons and protons together . It is more intense than electromagnetic, but has much less range.
  • Weak nuclear force. It is the force responsible for radioactive decay, capable of carrying out changes in subatomic matter, with an even lesser scope than strong nuclear forces.

Force units

According to the International System , force is measured in units called Newtons (N) , in honor of the great British physicist. These units correspond to 100,000 dynes and are understood as the amount of force applied during one second to a mass of one kilogram, so that it acquires the speed of one meter per second . That is, that: 1 N = (1kg x 1m) / 1 s 2 There are other units for other metric systems, which are equivalent, in Newtons, to:

  • 1 kilogram-force or kilopond is equal to 9.81 N
  • 1 pound-force equals 4.448222 N

How is force measured?

Today there are various models of dynamometers, even with digital displays.

The dynamometer is the ideal device for force measurement . It is also used to calculate the weight of objects. It was invented by Isaac Newton himself, using the stretching of a spring and Hooke's Law of Elasticity , in a similar way to a spring balance. Modern versions of the dynamometer follow the same principle and have hooks or rings at the ends of its cylindrical body, inside which there is a spring or spiral that acts as a spring. The force measurement will be marked at one of its ends (in some cases it may even appear on a digital screen).

Examples of strength

There are constantly examples of strength all around us. By exerting our muscular force on an object to lift it, we are defeating the force of gravity. If we push a massive body with the shoulder , like a refrigerator, we will not only have to overcome gravity , but also the friction force that opposes the movement. The same happens when we stick a refrigerator magnet , since the magnetic force holds it in place, but if we bring it closer to another magnet through the same pole, on the other hand, we will notice a tenuous repulsive force, which is another character of the same force. magnetic.

Force and motion

Force and motion are strongly involved with each other. In the first place, because force is that which is capable of starting, stopping or modifying a movement . For example, when a baseball crashes against the bat, the batter's force is printed on the second to deflect its trajectory (the same that the pitcher's force initially gave it, since the ball is normally at rest) and throw it away in the field. Whenever there is a force on a body in the same direction as the displacement, there will be work done by that force. The work required for this movement to occur is equal to the energy required to move the body. Depending on the type of force and the type of movement, various mathematical formulas will be available to calculate them. Follow in: Movement

Force of gravity

Gravity can be overcome momentarily through other forces.

The force of gravity is that attractive force that the masses exert on the matter around them , with an intensity proportional to their mass and inversely proportional to the distance that separates them. In fact, the Sun attracts our planet from a distance, with the same kind of force with which it attracts us, who live on its surface. Gravity can be overcome momentarily, as we do when jumping, but we will eventually succumb to it. Everything that goes up freely, has to come down.

Intermolecular forces

They are those that hold the molecules together , forming more complex and higher mass structures, depending directly on the nature of the atoms involved. That is why they are also known as intermolecular junctions or atomic junctions. These forces can be of two types: the Van der Waals Forces or the Hydrogen Bridges. Follow with: Dynamics

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