Forces – all about it

This article is about Forces. In this article you will find out what this is all about, which terms and formulas are important to you and how you can use them in examples. We can assign the chapter to mechanics and thus to the subject of physics.

Basic mechanics

In physics we often stumble over the concept of force. But what exactly is a force and in which subject areas do we actually use it? Before we take a closer look at the term force, let us first clarify the question in which areas of mechanics it plays a role.

As we already know from the Mechanics chapter, classical mechanics generally deals with bodies at rest and in motion and the forces that occur as a result. Two major sub-areas can be distinguished: the kinematics and the dynamics.

Figure 1: Mechanics classification

In kinematics, the study of movements, mechanical movements are considered without considering the acting forces. An example of this would be a uniform motion of a body where the cause of the motion is irrelevant. The second major topic is the dynamics. In this sub-area, attacking forces are also taken into account, which is why the dynamics are also called doctrine of forces is titled. This can be further subdivided into the sub-area of staticsin which forces on bodies at rest are treated and in the subfield of kinetics, in which forces are examined as the cause of the movements. When it comes to forces, we are in mechanics in the sub-area of ​​dynamics.

Powers – what is it all about?

Forces accompany us every day in everyday life. We encounter forces both when just standing on the ground and when throwing a ball. But what exactly is a force in physical terms?

description of a force

A force can usually only be visually identified by its Effect recognize. This definition of a force goes back to the well-known scientist Isaac Newton (1643 – 1727). Correspondingly, in literature, the power is associated with the letter f and the associated unit Newton marked after their inventor.

A force is often measured by a so-called spring dynamometer. This has a spring inside which, depending on the size of the pulling force, is pulled apart. With the help of a suitable scale, the acting force can be read off directly.

From a physical point of view, however, not only a numerical value and its associated unit are necessary for the description of the force.

To illustrate these different components, they are drawn in the graphic below. First, we start with a certain starting point or attackpoint. From there the line of action of the force are transferred to the sketch, i.e. along which line the force actually acts on the body. How big is the power (the amount), is determined by drawing an arrowlength Are defined. Finally the sense of direction added in the form of an arrowhead. In this way we get a force arrow with a certain length and a certain direction.

Mathematically, therefore, the force is marked with an arrow above the letter F. So this as directed Size defined as you could just see in the example. However, in the literature, the amount is often only used if it is permissible for the task.

Newton’s axioms

In this context, Isaac Newton, in addition to describing a force, also formulated various principles relating to forces. The so-called Newton’s axioms or Newtonian principles form an important foundation in the mechanics. In the literature, three different Newton’s laws are mainly mentioned, which we will briefly discuss below.

1. Newton’s axiom («lex prima»)

Newton’s first axiom, too law of inertia or. axiom of inertia, goes back to the definition of force. It states that the state of motion of a body not changedas long as no external acting forces cause a change of state.

2. Newton’s axiom («lex secunda»)

That principle of actionalso known as Newton’s second law or Newton’s lawalso goes back to the definition of force and establishes the connection between physical quantities. The unit results in a relationship between the quantities mass, acceleration and force.

3. Newton’s axiom («lex tertia»)

The 3rd Newton’s law, the so-called interaction law or reaction principle states that forces always occur in pairs.

When body A exerts a force on body B, body B exerts an equal but opposite force on body A. This is not to be confused with the balance of power, which we will discuss later in the article.

Superposition principle (4th Newton’s law «lex quarta»)

Because of superposition principle Is it at all possible to add several acting forces to a resulting force.

More information on the basics of force and the associated Newton’s axioms can be found in the chapter on force and the associated sub-chapters of Newton’s laws.

gravity

Gravity or gravity acts as attraction between two crowds and works over very long distances. The best-known example of this is gravity. It ensures that all bodies on earth and the earth attract each other. This is how it is possible to walk on the surface of the earth instead of floating around. She owns one infinite range and also cannot be shielded. It is still the weakest of all four fundamental basic forces, which is why we can, for example, pick up a stone from the ground relatively easily. In the literature, the gravitons are often mentioned as exchange particles, which ensure that the gravitation is transferred.