Strength is the dynamic agent responsible for changing the state of rest or movement of a body. When a force is applied to a body, it can develop a acceleration, as the Newton's laws, or deform. There are different types of force in nature, such as the strengthgravitational,strengthelectric,strengthmagnetic,strengthnuclearstrong and weak,strengthof friction, buoyant force etc.
forces are vector quantities which, therefore, need to be defined according to your module,direction and sense. The modulus of a force refers to its intensity; The direction it concerns the directions in which forces apply (horizontal and vertical, for example); each direction, in turn, presents two senses: positive and negative, left and right, up and down, etc.
Types of force
According to International System of Units, regardless of its nature, the force quantity is measured in the unit of kg.m/s², however, we usually use the magnitude newton (N) to designate such a unit, as a tribute to one of the greatest physicists of all time:
Isaac Newton. Devices used to measure forces are called dynamometers – springs of known elastic constants that stretch as some force is applied to them.Do not stop now... There's more after the advertising ;)
In some textbooks, it is common to define two types of strength: forces at a distance, also known as field forces, and contact forces. In the group of forces at a distance, it is customary to include the weight force, the magnetic force, the attraction force between charges and others. In the group of contact forces, examples are used such as pushing or pulling something, applying traction, frictional forces, among others.
Despite the proposed definition, it is necessary to clarify that there are no contact forces. All forces in nature arise through the interaction of different fields, such as the gravitational field and the electromagnetic field.
Even when we touch something, there is no contact between our hand and the object: on the microscopic scale, atoms do not touch, since, when very close, their electrospheres are deformed, repelling each other thanks to the charge of their electrons, which move apart due to the interaction of your electric fields and magnetic. There are few cases in which atomic nuclei actually touch. These situations involve very highquantitiesinenergy, as those obtained in experiments carried out inside particle accelerators.
Lookalso:Understand what happens when particles collide at speeds close to that of light
Let's see what types of forces exist in nature. From the forces described below, all known physical phenomena arise. Check out what they are and their main features:
- gravitational force: also known as strength weight, is the type of force that causes two bodies that have mass to attract each other. The weight force is responsible for keeping us tied to the Earth and also for the orbit of all the planets around the Sun.
- Electric force: is responsible for attracting or repulsing electrical charges. Chemical bonds, for example, only happen because of the difference in charge between atoms. The electrical force can cause the electrons present in the conductors move in a specific direction, giving rise to electrical currents, which, in turn, can be used to power electric circuits.
- Magnetic force: acts on moving loads. This type of force causes magnets to attract or repel each other, depending on the polarities of the magnetic field. THE magnetic force it also makes small magnetized needles orient themselves according to the direction of the Earth's magnetic field.
- Strong and weak nuclear force: are responsible for maintaining the integrity of the nuclei of atoms. The strong nuclear force keeps the protons attracted even though their charges repel each other. The weak nuclear force, in turn, holds the quarks together, giving rise to protons and neutrons, for example.
Forces like traction,friction,pushes,tugs,twists,forceselastic and others, generally described as forcesmechanics, they are, in fact, macroscopic manifestations of interactions that are mostly electrical.
Lookalso:Quantum Physics: a branch of Physics that studies small-dimensional phenomena
Newton's Forces and Laws
The concept of force can be somewhat vague if there are no expressions capable of defining it in a coherent way. Newton's laws are the set of laws that define what the forces are and what the behavior is.
According to the Newton's 1st Law – the law of inertia, if no force acts on a body, or if the forces acting on a body cancel each other out, this body can either be at rest or in a straight and uniform motion.
In addition to Newton's first law, the fundamental principle of dynamics, known as the Newton's 2nd Law, states that the net force on a body is equal to the mass of that body multiplied by the acceleration produced by the net force. Furthermore, the acquired acceleration must always be in the same direction and with the same direction as the resultant of the forces.
THE Newton's third law, known as the law of action and reaction, states that forces always arise in pairs. If body A exerts a force on body B, body B produces on body A a force of equal magnitude and direction, but in the opposite direction. In addition to indicating that the action and reaction forces are of equal magnitude, Newton's third law also states that the action and reaction pair can never occur in a single body.
Check out some examples where we can observe the law of action and reaction:
- When we walk, we push the ground backwards. The ground, in turn, pushes us forward.
- If we want to climb a rope, we must pull it down so that we can be pushed up.
- If, when immersed, we push the edge of a pool, we are pushed back. We do not observe this behavior out of water due to the frictional force that keeps us attached to the ground.
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fictitious forces
Forcesfictitious they are present in non-inertial frames. Newton's laws are defined exclusively for referentialinertials, that is, positions that are at rest or in rectilinear motion, with constant velocity. Situations involving rotations, for example, induce the emergence of fictitious forces, which are not actually forces.
When we go into high gear in a very sharp turn, we can feel our body squishing against the walls of a car. Another example is when we are sitting in a plane taking off, we can feel a “force” pressing us against the seat. This force is actually the inertia of the bodies.
Since a body is subject to acceleration, your inertiatends to resist this force, in this way, we feel a fictitious force in the opposite direction, which, in fact, is our tendency to remain in the state of movement we are in. .
A good example of fictitious force is centrifugal force. When in circular motion, bodies tend to escape in the direction tangent to the curve, as when we spin a stone on a string and release it. That strengthapparent, which causes the stone to hold the string taut, is actually the inertia of the stone itself manifesting itself against the application of a real force, called centripetal force.
The centripetal force, in this case, is produced by the pull that the string makes on the stone and it is, therefore, a real force, which always points to the center of the trajectory in which the stone moves. THE centrifugal force it is not, in fact, a force, but the expression of the inertia of the accelerated body.
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Formulas used for calculating forces
Check out the formulas that can be used to calculate different types of forces:
→ Force weight or gravitational force
G – universal gravitation constant (6.67.10-11 m³kg-1s-2)
r – distance from the center of the Earth (m)
Gravitational force and weight are synonymous. In the formulas above, we express the formulas used to calculate the gravitational force caused by two masses m and M and also the weight P, which arises due to the gravitational field. g of a star. Thus, we can understand that the gravitational force arises from the interaction between masses and gravitational fields.
→ Electric force
k0 – electrostatic vacuum constant (9.109 N.m²C-2)
AND – electric field (N/C)
r – distance between charges (m)
The gravitational force can be calculated very similarly to the gravitational force. Furthermore, it can be calculated in relation to the electric field.
→ Magnetic force
The magnetic force arises from the interaction of an electric charge q, with velocity v, in relation to a magnetic field B. The angle θ in the formula is measured between the velocity and the magnetic field.
→ Friction force
μ - coefficient of friction
N - Normal strength
The friction force arises as a result of molecular attractions, such as dipole-induced forces, also known as van der Waals forces.
→ Elastic strength
k - elastic constant (N/m)
x - deformation (m)
Elastic force arises when a body tends to return to its original shape when subjected to the application of an external force.
→ buoyant force
d – density (kg/m³)
g – gravity (m/s²)
V – submerged volume (m³)
The buoyant force arises when some body is inserted into a fluid, such as atmospheric air or water.
Despite being different from each other, all the forces exemplified above are dimensionally coherent, that is, they are all measured in the same unit, the newton.
By Me. Rafael Helerbrock
