Inertia – meaning and definition

Last updated on April 2nd, 2023 at 12:52 pm

In this post, we discuss the meaning and definition of inertia. Inertia is an important concept in the kinematics chapter of physics. Understanding it helps us to get an idea of the inertial frame of reference.
We will also see how mass is related to inertia. And, finally, we will study one example to understand inertia.

What is Inertia | Inertia definition

Here we get the definition of inertia. Inertia is the inherent property of an object by virtue of which it tends to retain its state of rest or motion.

From Newton’s first law of motion, we get the definition of inertia. As per this law, an object can’t change its state of motion by itself.

Inertia meaning

If the object is static (i.e. the object is in the state of rest) it will continue to be in the state of rest unless an external force is applied to it. Similarly, If the object is in a state of motion (object is moving in some direction) it will continue to move with the same speed without changing its direction unless an external force is applied to it. This tendency is termed Inertia in Kinematics.

mass and inertia

Mass is the measure of the inertia of an object. An object with more mass will have more inertia than an object of lower mass. In other words, a 10 kg object will have more tendency to retain its state of motion or rest than an object of 5 kg mass. That is why we need to apply more force to move or stop an object with more mass.

Also, read inertial and non-inertial frames of reference

Inertia example

Example: We need a larger force to set a loaded trolley in motion than an unloaded trolley. Similarly, we need more force to stop a loaded trolley than the unloaded one, if both have equal initial velocity.