Newton’s Laws of Motion

These three laws of motion are very important. They describe the relationship between forces that act on a body and the actual motion of that body. These laws have been verified by experiments and observation for  over two hundred years and have been found to hold true.

Newton’s First Law of Motion:

A body at rest tends to remain at rest, and a body in motion tends to remain moving at the same speed and in the same direction.

This simply means that a body will never start moving or stop until and unless an external force is applied to it.

An aircraft flying in straight and level will continue in the same flight path until an external disturbance (eg. elevator down) will cause it to change direction or velocity

Newton’s Second Law of Motion:

When a body is acted upon by a constant force, its resulting acceleration is inversely proportional to the mass of the body and is directly proportional to the applied force.

A force applied to a body, will produce proportional acceleration. If the same amount of force we to be applied to two aircraft of different weights, the lighter aircraft would have more acceleration.

Remember the formula

Force = Mass X Acceleration

Newton’s Third Law of Motion:

Whenever one body exerts a force on another, the second body always exerts on the first, a force that is equal in magnitude but opposite in direction.

This law explains that every action will have an equal and opposite reaction. The action of propellers pushing air backwards, there is an equal and opposite reaction which causes the aircraft to move forward.