# #7. Couple Moment what exactly is it?

### What is a Couple Moment?

A couple is defined as two parallel forces that have the exact same magnitude, but opposite direction, and they are separated by a perpendicular distance d.

**M= r x F**

Where,

r is the position vector directed between the two forces

M is the couple moment

F is the line of action of force

#### Important things to note:

- The resultant force on the system is ZERO
- It only causes Rotational movement

There are a couple of ways to solve such problem.

#### 1. Scalar Formulation

**M=Fd**

F is the Magnitude for force.

d is the Perpendicular distance between the couple.

Scalar Formulation is primarily used to solve 2D couple moment problems. There are certain situations in 3D where it is feasible to use this formula. NOTE: the values here are to be treated as scalar quantities.

#### Vector Formulation

**M= r x F**

F is the line of action of force.

M is the couple moment.

r is the position vector directed between the two forces.

For better understanding of the topic please visit my previous lecture.