Newton's 1st Law
Every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it.
-Newton
Sir Isaac Newton first presented his three Laws of Motion
in the "Principia Mathematica Philosophia Naturalis" in
1686.
Newton's first law of motion states that every object
will remain at rest in uniform motion in a straight line
unless compelled to change its state by the action of an
external force. This is also known as inertia.
The key point of this is that if there is no net force
acting on an object, the object will keep a constant
velocity. If the velocity is zero, the object
remains at rest.
Examples of Newton's First Law:
- 1- Motion of an airplane when the
pilot changes the throttle setting of the
engine.
- 2- Motion of a kite when the wind
changes
Although if there is an external force applied, the velocity will change and this change in velocity is determined by his second law.