What is rate

Kinetics, derived from the Greek word kinesis for movement, is a sub-area of ​​mechanics. It describes how quantities of movement, i.e. path, acceleration and speed, change under the action of forces in space.

The counterpart to kinetics is statics: Its area is the equilibrium of forces in non-accelerated bodies. Together, kinetics and statics form dynamics, the discipline that researches the effects of forces. This nomenclature is mainly used in technical mechanics. Physics, on the other hand, mostly uses the term dynamics instead of kinetics. The geometric description of the movement is sometimes incorrectly referred to as kinetics. However, this method is called kinematics.

Kinetics distinguishes between two dynamics of movement: there is the dynamics of advancing movement (translation) and the dynamics of rotary movement (rotation).

The fundamentals of kinetics were worked out by Galileo and Newton. In 1638 Galileo formulated the law of inertia. Newton's fundamental laws, the quintessence of his reflections on physics, date back to 1687. They provide the scientific basis for kinetics.

Important rates of kinetics

The equation of motion can be set up using the theorems of kinetics. This happens depending on the freely selectable generalized coordinates.

Center of gravity / momentum theorem

The basic law of dynamics is one of the best-known principles of dynamics. It is also called the principle of the center of gravity or the principle of momentum.

F - force 239
a - acceleration [m / s2]
m - mass [kg]

F stands for force, m for mass, a for acceleration. This equation can only be established if the mass m is constant over time. If there is a time-variable mass, the force is defined in terms of time, namely as the derivative of the momentum p = m • v:

v - speed [m / s]
p - impulse [Ns]
m - mass [kg]
t - time [s]

Performance rate

Even non-conservative systems that have a degree of freedom can be described using the principle of performance of mechanics.

E - energy [J] or [Nm]
t - time [s]
P - power [W] or [Nm / s]

The power of a force

The definition of the power of a (vectorial) force F is as follows:

P - power [W] or [Nm / s]
F - force 239
v - speed [m / s]

The achievement of a moment

A (vectorial) moment results in its performance as

P - power [W] or [Nm / s]
M - moment [Nm]
ω - angular velocity [rad / s]

Energy law

The energy law of mechanics can be derived as a special case from the power theorem for conservative systems.

E.kin - kinetic energy [J] or [Nm]
E.pot - potential energy [J] or [Nm]
t - time [s]

Working set

The fourth possibility for determining the equation of motion of a dynamic system is formulated by the working set.

W - work [J] or [Nm]
F - force 239
s - way [m]