Modern Physics

The 31 types of strength in physics and their characteristics

There are different types of force, depending on the direction, magnitude or intensity, application and direction. Force is any agent that has the ability to change the state in which a body is, regardless of whether it is in motion or at rest.

Force can also be an element that causes the deformation of a body. In the field of physics, it can be defined as a vector magnitude that is responsible for measuring the intensity of the linear momentum exchange between the elements. To measure force it is necessary to know its units and values, but also where it is applied and in which direction.

To plot the force graphically, you can choose a vector. But this must have four basic elements: sense, point of application, magnitude or intensity, and straight line of action or direction.

Types of Forces in Physics

There are several types of forces, some referred to as fundamental forces of nature and others that are expressions of these basic interactions.

fundamental forces:  gravitational force

This is one of the best known forces, mainly because it was one of the first to be studied. It is the force of attraction that is generated between two bodies.

In fact, the weight of a body is due to the action exerted by the Earth’s gravitational pull on it. The force of gravity is conditioned by the distance and mass of both bodies.

The law of universal gravitation was discovered by Isaac Newton and published in 1686. Gravity is what allows bodies to fall to Earth. And it is also responsible for the movements observed in the Universe.

That is, the fact that the Moon orbits the Earth or that the planets orbit the Sun is a product of the gravitational force.

electromagnetic force

The second everyday force is electromagnetic interactions, which include electrical and magnetic forces. It is a force that affects two bodies that are electrically charged.

It is produced with greater intensity than the gravitational force and is also the force that allows chemical and physical modifications of molecules and atoms.

Electromagnetic force can be divided into two types. The force that occurs between two charged particles at rest is called the electrostatic force. Unlike gravity, which is always a force of attraction, here the force can be both repulsion and attraction. But when a force arises between two particles that are in motion, another force called magnetic is superimposed.

Strong nuclear interaction

It is the strongest type of interaction that exists and is responsible for uniting the components of atomic nuclei. It acts in the same way between two nucleons, neutrons or protons and is more intense than the electromagnetic force, although it has a shorter range.

The electrical force present between the protons makes them repel each other, but the great gravitational force that exists between the nuclear particles makes it possible to combat this repulsion in order to maintain the stability of the nucleus.

Weak nuclear interaction

Known as a weak force, this is the type of interaction that allows for beta decay of neutrons. Its scope is so short that it is only relevant on a central scale. It is a force less intense than the strong one, but more intense than the gravitational one. This type of force can cause attractive and repellent effects, in addition to generating modifications in the particles involved in the process.

directed forces

In addition to the classification of main forces, force can also be divided into two important categories: distance forces and contact forces. The first is when the surface of the bodies involved is not rubbed.

This is the case of the force of gravity and the electromagnetic force. And the second is a direct contact between bodies that physically interact as when pushing a chair.

Contact forces are this type of force.

Normal force

This is the force exerted by a surface on an object that is supported by it. In this case, the magnitude and direction of the body are exerted in the opposite direction to the body on which it rests. And the force acts perpendicularly and externally from that surface.

That’s the kind of strength we see when we lean a book on a table, for example. There, the object is at rest on the surface and in this interaction are the weight and the contact force, the only ones that act.

applied force

In this case, it is the force that an object or human being transfers to another body, be it another object or another human being. The applied force always acts directly on the body, which means that direct contact always takes place. This is the type of force that is used when a ball is kicked or when a box is pushed.

tensile strength

This is the type of force that occurs when a spring, compressed or stretched, seeks to return to its state of inertia. These types of objects are meant to return to a state of equilibrium and the only way to achieve it is through force.

The movement occurs because this type of object stores an energy called potential. And this is what exerts the force that returns it to its original state.

magnetic force

This is a type of force that emerges directly from the electromagnetic force. This force arises when electrical charges are in motion. Magnetic forces depend on particle velocities and have a normal direction in relation to the velocity of the charged particle on which they exert their action.

It is a type of force that is linked to magnets, but also to electrical currents. It is characterized by producing attraction between two or more bodies.

In the case of magnets, they have a south end and a north end, and each attracts the opposite ends to each other on another magnet. Which means that while equal poles repel, opposites attract. This type of attraction also occurs with some metals.

electric force

This is the type of force that occurs between two or more charges and their intensity depends directly on the distance between these charges and their values.

As in the magnetic force with the same poles, charges that have the same sign will repel each other. But those with different signs will be attracted. In this case, the forces will be more intense, depending on the proximity of the bodies.

Frictional force

This is the type of force that occurs when a body slides over a surface or tries to do so. Frictional forces never help the movement, which means they are opposed.

It is basically a passive force that tries to slow down or even impede the movement of the body, regardless of the direction taken.

There are two types of friction force: dynamic and static.

Dynamic forces of friction

The first is the force required for the movement of two interacting bodies to be uniform. This is the force that opposes the movement of the body.

Static frictional forces

The second, static force, is what sets the minimum force necessary to move a body. This force must be equal to the surface with which the two bodies involved in the movement make contact.

The friction force plays a fundamental role in everyday life. As far as static friction is concerned, it is a very useful force, as it is what allows human beings to walk as they walk and it is also what allows the action of holding a pencil.

Without this force, there would be no wheeled transport as it is known today. Dynamic friction is of equal importance, as it is the force that stops any moving body.

tension force

This is the type of force that is applied when a rope, string, spring, or cable is tied to a body and subsequently pulled or tensioned. This interaction occurs parallel to the attached object and exits in the opposite direction.

In this case, the tension force value is equivalent to the tension value of the cable, spring, cable etc., at the moment the force is applied.

drag aerodynamic force

This type of force is also known as air resistance, because it is the force exerted on the body as it travels through the air. The aerodynamic drag force creates opposition so the body is difficult to advance through the air.

This means that the resistance placed by the object is always in the opposite direction to the speed of the body. Anyway, this type of force can only be perceived – or perceived more clearly – when dealing with large bodies or when moving at high speed. That is, the lower the speed and size of the object, the lower its resistance to air.

push up

This is the type of force that occurs when a body is submerged in water or any other liquid. In this case, the body appears to be much lighter.

This is because when submerging an object, two forces act at the same time. The weight of the body itself, which pushes you down, and another force that pushes you from below upwards.

When this force occurs, the contained liquid rises because the floating body displaces some of the water. On the other hand, to know whether a body is capable of floating, it is necessary to know what its specific weight is.

To determine this, weight must be divided by volume. If the weight is greater than the thrust, the body will sink, but if it’s less, it will float.

binding strength

If you want to determine the net force that exerts an action on a particle, you need to look at another type of force, that of ligation. A material point is said to be tied when there are physical problems that limit its movement.

It is these physical limitations that are called ligatures. This type of force produces no movement. On the contrary, its function is to prevent movements that produce active forces that are not compatible with ligatures.

molecular force

This type of force does not have a fundamental character like the first four basic forces, nor does it derive from them. But it’s still important for quantum mechanics.

As the name implies, molecular force is what acts between molecules. These are manifestations of the electromagnetic interaction between the nuclei and electrons of one molecule with those of another.

inertial force

Forces that can be identified with the body responsible for acting on the particle are known as real forces. But in order to calculate the acceleration of these forces, a reference element that must be inert is needed.

The inertial force is then that which acts on the mass when a given body is subjected to acceleration. This type of force can only be observed in accelerated reference systems.

This type of force is what keeps astronauts glued to their seats when a rocket launches. This force is also responsible for throwing a person against the car’s windshield during an accident. The inertial forces have the same direction but a direction opposite the acceleration to which the mass is subjected.

-According to specific parameters


Force acting on all particles in a given body, such as magnetic or gravitational forces.


They only act on the surface of a body. They are divided into distributed (weight of a beam) and punctual (when hanging a pulley).


The body exerting the force comes into direct contact. For example, a machine that pushes a piece of furniture.

the distance

The body exerting the force does not come into contact. They are gravitational, nuclear, magnetic and electrical forces.


The direction and intensity of the force changes little, like the weight of snow or a house.


The force acting on the object varies rapidly, such as in impacts or earthquakes.


Forces whose directions are contrary. For example, when two cars of the same weight and with the same speed collide.


For example, when a truck collides with a small car. The truck’s strength is greater and therefore they are unbalanced.


These are forces that are always present. For example, the weight of a building or a body.


Forces that can appear and disappear, like the wind.

Of action

Force exerted by one object that moves or modifies another. For example, a person who hits a wall.


The body to which the force is applied exerts a reaction force. For example, a wall, when hit, exerts a reaction force.

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