Newton's 1st Law
Law of Inertia
What is Newton's 1st Law of Motion?
Newtons 1st Law of Motion (Newton's Law of Inertia) states that an object at rest or in motion will stay this way unless acted on by an unbalenced force. To clarify, the definition of staying in motion is to move in a straight line at a constant speed.
Inertia measures an object's tendency to remain at rest or keep moving at a constant speed. The amount of inertia an object has depends on its mass. If an object has more mass then it will have more inertia.