Inertia

Inertia is a basic concept in Newton's First Law of Motion. It means the tendency of an object to resist any change in its state of motion or rest. In simple words, an object will remain at rest or continue moving in a straight line at constant speed unless an external force acts on it.

For example, when a bus suddenly stops, passengers tend to move forward. This happens because their bodies were in motion and try to continue moving—this is inertia. Similarly, when you quickly pull a card from under a coin, the coin falls straight down into the glass due to inertia of rest.

There are three types of inertia:

Inertia of Rest – An object at rest stays at rest (e.g., a book on a table).

Inertia of Motion – A moving object continues moving (e.g., a rolling ball).

Inertia of Direction – An object resists change in direction (e.g., turning a bike).

Mass is directly related to inertia. Objects with more mass have more inertia, so they resist changes more strongly.

Thus, inertia helps us understand why objects behave the way they do in everyday life.