The physical quantity that characterizes the measure with which other bodies or fields act on the body is called force. According to Newton’s second law, the acceleration that a body receives is directly proportional to the force acting on it. Accordingly, in order to change the speed of the body, it is necessary to influence it by force. Therefore, the statement that the forces in nature are the source of any movement is true.
Inertial reference systems
Forces in nature are vector quantities, that is, they have a modulus and direction. Two forces can be considered identical only when their modules are equal and their directions coincide.
If the body is not affected by forces, and also in the case when the geometric sum of the forces acting on the given body (this sum is often called the resultant of all forces) is equal to zero, then the body either remains at rest or continues to move in the same direction with constant speed (that is, it moves by inertia). This expression is valid for inertial reference systems. The existence of such systems is postulated by Newton's first law. There are no such systems in nature, but they are a convenient mathematical model. However, often when solving practical problems, the reference system associated with the Earth can be considered inertial.
Earth - inertial and non-inertial reference system
In particular, during construction work, when calculating the movement of cars and swimming vehicles, the assumption that the Earth is an inertial reference system is quite enough to describe the forces that are necessary for the practical solution of problems.
In nature, there are also problems that do not allow such an assumption. In particular, this applies to space projects. When the rocket starts straight up, it, as a result of the Earth’s rotation, makes visible movement not only along the vertical, but also in the horizontal direction against the Earth’s rotation. In this movement, the non-inertia of the reference system associated with our planet is manifested.
Physically, a rocket is not affected by forces deflecting it. Nevertheless, it is convenient to use inertia forces to describe the motion of a rocket . These forces do not exist physically, but the assumption of their existence allows us to imagine a non-inertial system as inertial. In other words, when calculating the missile trajectory, it is believed that the Earth reference system is inertial, but at the same time, a certain force in the horizontal direction acts on the missile. This force is called the Coriolis force. In nature, its effect becomes noticeable when it comes to bodies moving at a certain height relative to our planet for a fairly long time or at high speed. So, they take it into account, not only describing the movement of rockets and satellites, but also when calculating the movement of artillery shells, aircraft, etc.
Nature of interactions
All forces in nature, by the nature of their origin, belong to four fundamental interactions (electromagnetic, gravitational, weak and strong). In the macrocosm, only the effect of gravity and electromagnetic forces is noticeable. Weak and strong interactions affect the processes occurring inside atomic nuclei and subatomic particles.
The most common example of gravitational interaction is gravity. This is the force with which the Earth acts on the bodies around it.
The electromagnetic forces, in addition to the obvious examples, include all the elastic pressure-related interactions that the bodies exert on each other. Accordingly, such a force of nature as weight (the force with which the body acts on a suspension or support) has an electromagnetic nature.