Newton’s First Law – Alternative 
Statement 
In the absence of external forces, 
an object at rest remains at rest and an object in motion 
continues in motion with a constant velocity. 
Newton’s First Law describes what happens in the absence 
of a force. Does not describe zero net force 
Also tells us that when no force acts on an object, the 
acceleration of the object is zero Can conclude that any 
isolated object is either at rest or moving at a constant 
velocity 
The First Law also allows the definition of force as 
that which causes a change in the motion of an object.