Physics: Introduction to Forces and Force Composition

Vocabulary practice flashcards covering the definition of forces, vector and scalar notations, gravity, normal reaction, vector composition of concurrent forces, trigonometry decomposition, and force classifications.

Force

The action that a body undergoes or exerts on another body, which can deform the body or modify its state of rest or motion.

Characteristics of a force

The four defining properties of a force vector: point of application (point d'application), direction, sense (sens), and intensity (intensité).

Newton ($\text{N}$)

The unit of measurement for force in the International System of Units (SI).

Center of gravity

The point of a body where all forces acting upon it are considered to be applied in order to simplify force balance calculations.

Weight force ($G$)

The force exerted on an object due to terrestrial attraction, calculated as $G = m \times g$, where $m$ is the mass in kilograms ($\text{kg}$) and $g$ is terrestrial acceleration.

Terrestrial acceleration ($g$)

The acceleration caused by Earth's gravity, equal to $9.81\,\text{m/s}^2$.

Normal reaction force ($R$)

The supporting contact force exerted by a surface (such as the ground) perpendicular to the contact interface.

Vector notation

A mathematical representation of a force (denoted with an arrow, such as $\vec{F}$) that accounts for its intensity, direction, and sense.

Scalar notation

A numerical representation of a force (denoted without an arrow, such as $F$) that accounts solely for its magnitude or intensity.

Resultant force ($F_3$)

The combined single force resulting from the vector addition of two concurrent forces: $\vec{F}_3 = \vec{F}_1 + \vec{F}_2$.

Composition of forces with identical direction and sense

A case where two forces act along the same line in the same direction, yielding a resultant scalar intensity of $F_3 = F_1 + F_2$.

Composition of forces with identical direction and opposite sense

A case where two forces act along the same line but in opposite directions, yielding a resultant scalar intensity of $F_3 = F_1 - F_2$.

Composition of perpendicular forces

A case where two forces act at a right angle ($90^\circ$), yielding a resultant scalar intensity calculated by the Pythagorean relation: $F_3 = \sqrt{F_1^2 + F_2^2}$.

Trigonometric force decomposition

The method of resolving an arbitrary force into orthogonal components using right-triangle trigonometry: $\sin(\alpha) = \frac{\text{CO}}{H}$ ($\text{CO} = H \cdot \sin(\alpha)$) and $\cos(\alpha) = \frac{\text{CA}}{H}$ ($\text{CA} = H \cdot \cos(\alpha)$), where $\text{CO}$ is the opposite side, $\text{CA}$ is the adjacent side, and $H$ is the hypotenuse.

Contact forces (Forces de contact)

Forces that act only when bodies physically touch each other, including muscular force, hydraulic force, Archimedes' buoyant force, friction force, and normal reaction force.

Distance forces (Forces à distance)

Forces that act between bodies without physical contact across a distance, including magnetic force, electric force, and gravitational force (weight).