Inertia: What students should know about this physics concept  

As fascinating as science can, there is no denying that it is also challenging, especially with concepts related to physics. Inertia is one such physics concept that students find it difficult to understand, theoretically. What makes it easier to grasp these concepts is using practical examples and comparisons which are easy to remember. Read on to find a simplified explanation of inertia to share with your school-goer, along with a few examples to help. 

What is inertia?  
The concept of inertia was explained by Sir Isaac Newton through his first law of motion. According to this law, an object at rest stays at rest while an object in motion continues to be in motion up until an external force acts on it. Essentially, inertia is the resistance exerted by a physical object in response to a change in its velocity. These changes could be in its speed, direction or motion. For example, when a ball is rolled on the floor, it will continue to roll until friction, a barrier, or any other obstruction comes in its way. 

What are the types of inertia? 
There are three basic types of inertia. These include: inertia of rest, inertia of motion and inertia of direction. 

Inertia of rest: When an object continues to stay where it has been placed, it is known as inertia of rest. Moreover, it will continue to stay there until some external force moves it. To put it simply, it is the tendency of the object to remain in the state of rest. For example, a tablecloth can successfully be pulled from underneath plates, if the action is done swiftly and quickly. As long as the friction from the movement of the tablecloth is not too much, the plates remain still. 

Inertia of motion: This type of inertia is defined as the inability of the object to change its state of motion by its own accord. Thus, an object will continue to move in motion at the same speed until an external force acts on it. For example, rolling a cart filled with bricks will be a smooth task if there are no external forces affecting it. However, if it encounters a stone or a bump along the way, the bricks will fall off. Here, the stone/ bump is the external force that interferes with the cart’s motion. 

Inertia of direction: According to this principle, an object will continue to move in the same direction until an external force acts on it. Thus, it is the property of an object to maintain a sense of direction. For example, if you add sugar to a cup of tea and stir it with a spoon and then remove it, the liquid will still continue to swirl due to the inertia of direction.