What are different types of mechanics

This article is about the different types of powers. The mechanical forces are listed, which are considered the basis in physics and mechanics and are of the greatest importance in mechanical engineering.

Weight force

The weight of a body is understood as the force with which the gravity acts on this body.

The greater the mass of the body, the stronger the gravitational pull of the earth. In addition, greater force is required to accelerate the larger the mass. If there is no air resistance, it happens that all bodies that are in free fall are accelerated at the same speed towards the center of the earth.


The value of the weight FG, which acts on a body of mass by means of the gravitational pull of the planet, is proportional to the acceleration due to gravity g.

Weight force on a body of mass m

Weight force = mass x acceleration due to gravity

F.G - Weight force 1214
m - mass [kg]
g - acceleration due to gravity [m / s2]

From the general law of gravitation it can be deduced that the following approximately applies to the spatial factor on the earth's surface: g = 9.81 N / kg


A body with a mass of 1 kg has a weight on earth of

Frictional force

Frictional forces occur wherever bodies touch or move against each other. Responsible for this: uneven body surfaces and cohesive forces that act between the molecules of the bodies that rub against each other.

Static friction

If you enlarge polished surfaces, even these look like a kind of mountain range with numerous elevations and sharp peaks. As soon as bodies adhere to one another, their respective tips hook into one another. Therefore, the attempt to move them against each other deforms these tips - so stronger tensile force counteracts even stronger adhesive friction force.
The more two bodies are pressed together, the greater the maximum possible static friction.

The static friction works as long as the two bodies (friction partners) do not move towards each other. As soon as the static friction is overcome, the bodies begin to move towards each other and fall into the area of ​​sliding friction.

Formula - static friction:

F.R, detention, max - Static friction 1214
µH - coefficient of static friction [kg]
F.N - normal force 1214

The constant of proportionality is called the coefficient of static friction µH. This depends on the material and surface properties of the respective body.

Sliding friction

When two bodies move against each other, their rough surfaces only rub on top of each other. In contrast to static friction, the bodies do not completely interlock here.

The sliding friction force FR, sliding is - like the static friction force - dependent on the pressing normal force F.N (mostly the weight) as well as the surface properties of the respective body.

Formula - sliding friction:

F.R, sliding, max - sliding friction 1214
µG - coefficient of sliding friction [kg]
F.N - normal force 1214

The coefficient of sliding friction is always smaller than the coefficient of static friction µH.

Frictional force - static friction & sliding friction

Rolling friction

When can uneven surfaces be overcome much more easily? Then when one body rolls on top of the other. With the same compressive force or the weight force, the rolling friction force is significantly smaller than the sliding friction force.

Formula - rolling friction:

F.R. - rolling friction 1214
cR. - coefficient of rolling resistance [kg]
F.N - normal force 1214

Frictional force - rolling friction

Flow resistance

When a body moves through a gaseous or liquid medium, it always has to overcome a flow resistance such as water or air resistance. The size of the drag force is influenced by the density ρ of the medium that the body traverses, its cross-sectional area, the square of its speed v2, but also the so-called "drag coefficient" cw, which quantifies how the respective body shape affects.

The following applies approximately to the drag force FL. the following formula:

F.L. - Air resistance 1214
cw - Resistance contributor, unified
A - cross-sectional area [m2]
ρ - density [kg / m3]
v - speed [m / s]

Clamping force or spring force

For example, if you compress an elastic body like a helical spring or pull it apart, an opposing force acts in this spring: This force tries to shape the spring in the direction of its original length.

The helical spring is thus compressed or stretched by a distance s. The further this distance s, the stronger the restoring clamping force FS. the coil spring.

Formula - clamping force / spring force:

F.S. - Clamping force / spring force 1214
k - Spring constant
s - spring travel [m]

The spring constant k is dependent on both the shape and the material of the helical spring - or of the elastic body.

Calculate spring force

Radial force

Because of its mass, a body always moves in a straight line, provided that no force acts on it. From this it follows that a circular movement can only be realized if a body is held on a circular path by a force which accelerates it continuously towards the center of the circle. The name of this force: radial force or centripetal force.

The radial force / centripetal force

More details on the calculation of the various mechanical forces and types of force.