# What is Inertia in Physics? A Comprehensive Guide

Inertia is a property of a body that allows it to oppose any force that attempts to set it in motion or change its speed. It is a passive property and does not allow a body to do anything except to resist active agents such as forces and torques. Before Newton's time, the dominant thought was that it was the natural tendency of objects to reach a resting position. It was believed that moving objects would eventually stop moving; a force was necessary to keep an object in motion.

Galileo, a first-rate scientist in the 17th century, developed the concept of inertia. He reasoned that moving objects eventually stop due to a force called friction. He conducted experiments using two planes inclined opposite each other and observed that a ball rolled along one plane and would rise up the opposite plane to approximately the same height. If softer planes were used, the ball would roll in the opposite plane even closer to the original height.

Galileo postulated that if friction could be completely eliminated, the ball would reach exactly the same height. Inertia is the quantity that depends solely on mass. The more mass, the more inertia. Moment is another quantity in Physics that depends on both mass and speed.

Momentum will be discussed in a later unit. If someone increases their mass, then their inertia increases as well. Bricks, like any object, have inertia; they will resist changes in their state of movement. Suppose there are two seemingly identical bricks resting on the physics reading table. However, one brick consists of mortar and the other brick consists of polystyrene foam.

Without lifting the bricks, how would you know which brick was the styrofoam brick? You could give bricks an identical thrust in an effort to change their state of motion. The brick that offers the least strength is the brick with the least inertia and, therefore, the brick with the lowest mass (i.e., styrofoam).Inertia is one of the main manifestations of mass, which is a quantitative property of physical systems. It is also one of the fundamental principles of classical physics that are still used today to describe the movement of objects and how they are affected by forces applied to them. In summary, inertia is a property of matter by which it remains in a state of rest or in uniform motion in a straight line unless some external force acts on it. Sir Isaac Newton's first law of motion is also known as the Law of Inertia and is one of the most important and recognized laws in physics.

Objects want to stay at rest or move unless an external force causes a change.