Three types of not moving

Not Moving is one of the most important concepts in Practical Method. There are 3 types of Not Moving. 

Absolutely Not Moving

• Also known as: Truely Not Moving
• This point is simply not allowed to move in any way.
• Example: A nail on the wall. The nail is not moving in any direction.

Relatively Not Moving

• Also known as: Structurally Not Moving
• Between two points, a constant relationshiop is maintained.
• Example: A passenger seating on the car going from place to place. The passenger is not moving relative to the car.

Restrictively Not Moving

• Also known as: Staying on the track
• This point is only allowed to move in a very specific way.
• Example: A train can only move along the track.  It works properly only when it does not derail.

 

Let's illustrate using Fig. 1.

Point A is absolutely not moving as it is not allowed to move at all.

Point B is relatively not moving as it's relationship with A and C respecitvely is fixed to the solid stick in between.

Point C is restrictively not moving as it is only allowed to move along the AC line.

If we pull point C to the right, point B will be affected indirectly and come down while A does not move at all.  In fact, B will rotate around A as a result.