Law of inertia

Definition

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

5 Must Know Facts For Your Next Test

1. The law of inertia applies to both objects at rest and objects in motion.
2. Inertia is directly related to the mass of an object; more massive objects have greater inertia.
3. An external force is required to change the state of motion of an object due to its inertia.
4. The concept explains why passengers lurch forward in a car when it suddenly stops.
5. Inertia is a fundamental principle that underlies Newton's other laws of motion.

Review Questions

• What does the law of inertia state about objects at rest and in motion?
• How does the mass of an object affect its inertia?
• Why do passengers move forward when a car abruptly stops?

Related terms

Force: A push or pull acting upon an object resulting from its interaction with another object. It can cause changes in the object's velocity.

Newton's Second Law: $F = ma$, where $F$ is force, $m$ is mass, and $a$ is acceleration. It describes how the velocity of an object changes when it is subjected to an external force.

Mass: A measure of the amount of matter in an object, typically measured in kilograms (kg). It quantifies the object's resistance to acceleration when a force is applied.