Newton’s first law

Definition

Newton's First Law, also known as the law of inertia, states that an object at rest will stay at rest and an object in motion will remain in motion at a constant velocity unless acted upon by a net external force.

5 Must Know Facts For Your Next Test

1. Newton's First Law is sometimes referred to as the law of inertia.
2. The law implies that if no net force acts on an object, its velocity will not change.
3. Inertia is the property of matter that resists any change to its state of motion.
4. The law applies to objects both at rest and in uniform motion in a straight line.
5. An example of this law is when passengers lurch forward in a car that suddenly stops; their bodies continue moving forward due to inertia.

Review Questions

• What does Newton's First Law state about an object's state of motion?
• How does inertia relate to Newton's First Law?
• Can you provide a real-world example that illustrates Newton’s First Law?

Related terms

Inertia:

The resistance of any physical object to a change in its state of motion or rest.

Net Force: The overall force acting on an object when all individual forces are combined.

Uniform Motion:

$\text{Motion}$ at a constant speed in a straight line.