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Wonders of Physics


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Vector Diagram – Parallelogram Method for 4 different kinds of questions

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.

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

Vector Diagram Parallelogram 01Vector Diagram Parallelogram 02Vector Diagram Parallelogram 03Vector Diagram Parallelogram 04

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.