# Evan's Space

## Wonders of Physics # Vector Diagrams

Vector diagram is commonly referred to parallelogram rule.

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 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.

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.

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.