4.1.1—Forces

Force has magnitude and direction. Resolve it into perpendicular components, add components to find the resultant, and use Newton’s law or equilibrium equations along each axis.

Draw a force diagram, choose positive directions, and keep units consistent. Equal and opposite forces act on different bodies and should not be cancelled across a single free-body diagram.

Forces (3,4) N and (−1,2) N have resultant (2,6) N with magnitude √40 N.

A scalar magnitude alone cannot determine a resultant; direction is part of the force.