Newton’s first law of motion

Definition

Newton’s First Law of Motion states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. This law is also known as the law of inertia.

5 Must Know Facts For Your Next Test

1. Inertia is the tendency of an object to resist changes in its state of motion.
2. An object at rest stays at rest, and an object in motion stays in motion with the same speed and direction unless acted upon by a net external force.
3. The concept of inertia was first introduced by Galileo Galilei before being formalized by Newton.
4. Mass is a measure of an object's inertia; the greater the mass, the greater the inertia.
5. Newton’s First Law applies to objects moving at a constant velocity as well as those at rest.

Review Questions

Related terms

Force:

A push or pull acting on an object that can cause it to accelerate. Measured in newtons (N).

Inertia:

The tendency of an object to resist changes in its state of motion.

Net Force:

The vector sum of all forces acting on an object. Determines whether and how an object's motion will change.