• Mechanics
  • /
  • Dynamics
  • /
  • Newton's laws

Once one knows the forces acting on an object, you can use Newton's laws to understand whether the body will be in movement and the characteristics of this dynamic.

For the application of such laws, it is necessary that the observer of the system stays in an inertial frame, that is, stationary or in uniform rectilinear motion. Accelerated referential require a different formulation. Initially, for ease, it is considered that the body can only move without rotating (translational motion). Using this formulation, for example, you cannot describe the motion of a ball that moves and also rotates. Therefore, we say that the body under analysis is treated as a particle.

Newton's Laws

\(1^a\) - Law of Inertia
If the resultant force acting on a body is zero, the body can only be at rest or in a uniform linear motion.
\(2^a\) - Fundamental Law of Dynamics
The acceleration acquired by a body is directly proportional to the resultant force and inversely proportional to its mass. This can be written as \(\vec{a} = \frac{\vec{F_{net}}}{m}\) or, in a more known form $$ \vec{F}_{net} = m \vec{a},$$ where \(\vec{F}_{net}\) is the resultant force acting on the system of interest.
\(3^a\) - Law of Action and Reaction
Every action has a reaction of the same module but in the opposite direction. In mathematical form: $$ \vec{F}_{a,b} = - \vec{F}_{b,a}, $$ where \(\vec{F}_{a,b}\) is the force that a body \(a\) does in a body \(b\) .


Dynamic Exams
Differentiated Content
Top approval rate