Work out net force instantly with clear inputs, formula shown and shareable results.
Forces add as vectors, so the resultant of two forces follows the parallelogram rule: sqrt(F1^2 + F2^2 + 2.F1.F2.cos theta). At right angles 40 N and 30 N give 50 N, not 70 N. Dividing by the mass gives the acceleration that resultant produces.
Resultant magnitude
F = sqrt(F1^2 + F2^2 + 2 F1 F2 cos theta)
Direction
tan(phi) = F2 sin theta / (F1 + F2 cos theta)
Because the forces do not point the same way. Only when the angle is zero do they add directly.
At 180 degrees the cosine is -1 and the resultant is the difference. Equal opposing forces give zero and the body stays in equilibrium.