**Vector diagram** is commonly referred to ** parallelogram diagram**.

Vector diagrams are generally divded into 3 categories:

**1)** 2 forces acting on a body, there is a resultant force. (Newton’s 2nd Law)

**2)** 3 forces acting on a body, the body is ** at rest / in equilibrium** or moving at

**. (Newton’s 1st Law, Net force = 0N)**

*constant speed*– The resultant force due to any 2 forces is ** equal and opposite** to the 3rd unknown force.

**3)** 3 forces acting on a body, the body is ** at rest / in equilibrium** or moving at

**(Newton’s 1st Law, Net force = 0N)**

*constant speed*– Only 1 known force, angles given, using ** closed loop triangle** to find the 2 unknown forces.

Let’s look at some examples for each category.

**1) 2 forces acting on a body, there is a resultant force. (Newton’s 2nd Law)**

**2) 3 forces acting on a body, the body is ***at rest / in equilibrium*** or moving at ***constant speed***. (Newton’s 1st Law, Net force = 0N)**

**– The resultant force due to any 2 forces is equal and opposite to the 3rd unknown force.**

**– You can either use ***parallelogram rule*** or ***closed looped triangle***.**

Example 1: Body at rest – Using Parallelogram Rule

Example 1: Body at rest – Using Closed-Looped Triangle

Example 2: Body at constant speed – Using Parallelogram Rule

Example 2: Body at constant speed – Using Closed-Looped Triangle

**3) 3 forces acting on a body, the body is ***at rest / in equilibrium*** or moving at ***constant speed*** (Newton’s 1st Law, Net force = 0N)**

** – Only 1 known force, angles given, using closed loop triangle to find the 2 unknown forces.**

Example 1

Example 2

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