For Combined Science Physics Olevel, when constructing vector diagram, a method called Parallelogram Method is commonly used.
Parallelogram Method is used when 2 forces are known, and the resultant (net) force R, can be found.
Below show 5 different variations of questions when can be solved by using Parallelogram Method:
(A) Body has acceleration, forces are unbalanced, there is a resultant force R (Newton’s 2nd law)
(B) Body at rest, all forces are balanced, there is no resultant force R (Newton’s 1st law)
(C) Body moving at constant velocity, all forces are balanced, there is no resultant force (Newton’s 1st law)
(D) Finding unknown force (with resultant force R + another known force are given)
(F) Vector diagram is applicable to all vector quantities (with magnitude and direction). Not just for forces.
For Pure Physics, another method is the closed-loop triangle, where only 1 known force with 2 other unknown force. Click here to view the video tutorials.