Mechanical engineering and physics are the same

Force is one of the central phenomena in physics. Its classic definition relates to the acceleration that a moving body experiences as a result of its action. In addition to acceleration, forces also cause deformations on bodies on which they act.

Mathematically speaking, forces are vectors. That is, they have an amount and a direction. A force that causes a body to move in its effective direction does work.

Relationship between force and energy

For the application of such forces, therefore, energy is necessary, which is supplied to the accelerated or deformed body. For example, a force can compress a spring, absorbing energy that it releases when the force is released. Like a number of other specific forces, this force has a special name in physics: the spring force or tension force.

However, not all forces are associated with an exchange of energy. Forces that do not do any work are, for example, holding forces that prevent movement, but also managers because the direction of force is perpendicular to the direction of movement. For this reason, bridges are usually supported on rollers, at least on one side, because such a floating bearing is only used by executives, neglecting the friction.

The unity of power

The international system of units measures force in Newtons, which is a composite unit made up of the basic units kilogram, meter and second. The definition is:

In formulas, forces are usually noted with a capital F, for example:

F - acceleration force 8716
m - mass [kg]
a - acceleration [m / s2]

Effect of a force

The effect of a force can manifest itself in different ways:

  • A force can change the direction of movement of a body
  • A force can change the speed of a body
  • Forces can deform other objects on impact, for example
  • A force acts in a certain direction (keyword: vector)

Types of forces

The history of force as a physical unit

The Englishman Sir Isaac Newton introduced the modern concept of force in physics in the 17th century with his three laws of motion. He recognized force as the cause of the change in the state of motion of a body, which is reflected in his definition of force as a change in momentum over time. The significant insight can also be traced back to Newton. that every force that one body exerts on another causes an equal but opposite counterforce. This is the basis of statics, which calculates loads in structures using the balance of the acting forces.

The balance of power

For the consideration of the balance of forces, their vector property is important. There is an equilibrium of forces when the vector sum of all external forces on a body is zero.

∑Fi = 0 The sum of all forces results in zero

You can visualize this in a two-dimensional model by entering the forces as arrows, the length of which corresponds to the magnitude of the force. If you join these arrows so that one end of the arrow comes to rest at the tip of another, a closed polygon is the result of an equilibrium of forces.


Forces at one point (left) are merged into a polygon (right) => equilibrium of forces

In the equilibrium of forces, a body does not change its state of motion, that is, it is at rest or moves with unchanged speed and direction. The state of motion does not change even with a circular motion with a constant rotational speed, although it represents a uniformly accelerated motion. But even with rotation, the centripetal force, which forces the body into the circular path, always acts perpendicular to the direction of movement.