Forces in nature

The physical quantity that characterizes the measure with which other bodies or fields are affected by the body is called force. According to Newton's second law, the acceleration that the body receives is directly proportional to the force acting on it. Accordingly, to change the speed of the body, you must act on it by force. Therefore, the correct assertion is that forces in nature are the source of any movement.

Inertial Reference Systems

Forces in nature are vector quantities, that is, they have a modulus and direction. Two forces can be considered equal only when their modules are equal, and their directions coincide.

If the force does not act on the body, and also when the geometric sum of the forces acting on a given body (this sum is often called the resultant of all forces) is zero, the body either remains at rest or continues to move in one direction with Constant speed (that is, it moves by inertia). This expression is valid for inertial frames of reference. The existence of such systems is postulated by Newton's first law. In nature, there are no such systems, but they are a convenient mathematical model. Nevertheless, often in solving practical problems the frame of reference associated with the Earth can be considered inertial.

Earth - inertial and non-inertial reference frame

In particular, for construction works, in calculating the movement of cars and swimming transport, the assumption that the Earth is an inertial frame of reference is 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 refers to space projects. At the start of the rocket, strictly upwards, due to the rotation of the Earth, it makes visible movement not only along the vertical, but also horizontally, against the rotation of the Earth. In this movement, the non-inertiality of the frame of reference associated with our planet is manifested.

Physically, the rocket does not have forces that deflect it. However, to describe the movement of the rocket it is convenient to use inertia forces. These forces do not exist physically, but the assumption of their existence makes it possible to represent a non-inertial inertial system. In other words, when calculating the trajectory of a rocket, it is considered that the reference system "Earth" is inertial, but a certain force in the horizontal direction acts on the rocket. This force is called the Coriolis force. In nature, its action becomes noticeable when it comes to bodies moving at a certain altitude relative to our planet for a fairly long time or at a high speed. So, it is taken into account, not only describing the movement of rockets and satellites, but also in calculating the movement of artillery shells, aircraft, etc.

Nature of interactions

All forces in nature by nature of their origin belong to four fundamental interactions (electromagnetic, gravitational, weak and strong). In the macrocosm, only the effects of gravity and electromagnetic forces are noticeable. Weak and strong interactions affect the processes occurring inside atomic nuclei and subatomic particles.

The most common example of gravitational interaction is the force of attraction. This is the force with which the Earth acts on the surrounding bodies.

Electromagnetic forces, in addition to the obvious examples, include all the elastic, pressure-related interactions that bodies exert on each other. Accordingly, such a force of nature as weight (the force with which the body acts on the suspension or support) is electromagnetic in nature.