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 n**o 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.

Click here to view video tutorials on how to construct parallelogram step-by-step

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.