## Dynamics theory

# Dynamics

Dynamics is the part of physics that describes the time evolution of a physical system in relation to the causes of changes in physical and/or movement state.

Dynamics’ aim is to describe factors that may cause alterations of a physical system, quantify them and raise equations of motion or evolution equations for that operating system.

** Dynamic Laws:** They were formulated by Isaac Newton and thanks to them we can predict the movement of a body if we know its current status and the forces which are acting on it.

**Inertia Law:**“If the result of the forces which are acting on a body is zero or does not exist any external force, it is that if the body is at rest, it is going to continue to do so and if he moved with rectilinear uniform movement, it will continue to move with that same movement.”**Fundamental Dynamics Law:**“If on a body is acting a resultant force, it acquires a acceleration that is directly proportional to the force applied, being the body mass the proportionality constant. This acceleration has the same direction as the resultant force

**Action and reaction principle:**“If a body exerts a force on another body, this one at the same time, turn exerts a force on the first one with the same magnitude and direction, but opposite.”

The negative sign means the opposite direction. The forces do not be cancelled because they act on different bodies.

** Hooke’s law:** A body is elastic when it regains its shape after stopping the forces that had deformed it. In the case of a spring, the deformation (elongation) is directly proportional to the applied force.

The elastic bodies have elasticity limits within which Hooke’s law is fulfilled, if these limits are exceeded, the body does not obey this law and its deformation can be permanent.

The dynamometer is based on this law.

**FORMULA SUMMARY:**

Fundamental equation of the Dynamics

Centripetal and centrifugal forces

**Tensions**

Object that rises

Object that goes down

Atwood machine

Friction (µ = coefficient of friction ; N = Normal Force)

Friction on a horizontal plane

Friction on an inclined plane

Radius of curvature with cant and friction

Mechanical impulse

Linear momentum or Quantity of movement

Theorem of the mechanical impulse

Angular or kinetic momentum

Theorem of the angular momentum

Hooke’s Law

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