Resultant force

The vector sum of all forces acting on a body, equivalent to those forces for its translational motion. Its magnitude and direction determine the body's acceleration through Newton's second law.

Vector addition: The operation of combining vectors by adding their corresponding components. Forces combine component by component to produce the resultant.
Force: An interaction that can change an object's motion or deform it. Resultant force combines individual forces of this kind.
Inclined plane: A flat surface set at an angle to the horizontal. Forces along and perpendicular to the slope determine an object's acceleration.
Torque: The rotational effect of a force about a point or axis, measured by its moment arm and magnitude. A force system can have zero resultant force yet still exert a torque.
Newton's second law: The law stating that an object's acceleration equals its net force divided by its mass. It connects the resultant force directly to translational acceleration.
Vector (physics): A physical quantity with both magnitude and direction, represented mathematically by a vector. Force is a vector, so direction matters when forces are combined.
Projectile motion: Motion under gravity after an object is launched, when air resistance is neglected. Its changing velocity follows from the gravitational resultant force.
Couple (mechanics): A pair of equal, opposite, parallel forces separated by a distance, producing a pure turning effect. A couple has no resultant force but does produce rotation.
Free-body diagram: A diagram showing an object and the external forces acting on it. It isolates the forces that must be added to find the resultant.
Mass: A measure of an object's inertia, or resistance to acceleration. The same resultant force produces different accelerations for different masses.

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Lami's theoremRelated: Equilibrium requires the resultant of the three forces to be zero.