Inertia

Introduction

Inertia is the resistance by any object to move and to change in velocity, motion, and direction. Inertia is adapted from the Latin word ‘iners’ meaning idle. 

Mass and inertia have a significant relationship. 

Mass is the measure of inertia of a body.

The inertia of any object will depend on this mass; the greater the mass of the body, the greater the inertia.

Inertia is better understood by the explanation given by Newton explaining inertia in his first law of motion. Newton’s first law of motion states that ‘an object will continue to be in the state of rest or in a state of motion unless an external force acts on it.’

The Inertia Principle:

Based on Galileo’s work, Sir Isaac Newton developed his first law of motion. He discovered that a ball rolling in a certain way takes a certain amount of effort to stop it once it has started moving in that direction. For the ball’s velocity and direction to alter, force must be applied. Newton’s definition of the Law of Inertia:

Newton writes in his Principia Mathematica that, “The velocity of bodies included in a given space is equal among themselves, whether that space is at rest or flows evenly forward in a straight line without circular motion”. If an object does not receive external force, it will be either at rest or moving. Newton’s Second Law of Motion derives the relationship among acceleration, force, and mass.

Newton’s Third Law of Motion defines that when a force is applied to one object, another equal force is used to the origin of the force. According to this law, every action has an equal and opposing reaction. For example, when someone pulls on a rope, it pulls back the one doing the pulling.

Sir Issac Newton was a renowned physicist who gave the world of physics the understanding of motion, force, and rest. These concepts were taken up by a lot of scientists and many hypotheses were proposed until Newton proposed the three laws of motion. These three laws gave a better understanding of forces that are present in nature, how bodies move and stay at the rest. 

The study of inertia was a vast subject that had to be understood for us to understand the movement of bodies, the forces in nature, gravitational pull, the movement of planets in the solar system, and much more.

Prior to the Renaissance, the Aristotelian theory of motion was the most widely accepted in Western philosophy, which maintained that “in the absence of external force, all objects would come to rest,” and that “moving objects only continue to move so long as there is a force helping them to do so.” Despite its widespread acceptance, the Aristotelian hypothesis has been criticised by several well-known philosophers. Galileo improved the theory of inertia later on.

Types of inertia:

  Inertia is mainly of three types: the inertia of rest, the inertia of motion, and the inertia of direction.     

 Inertia of rest:

Inertia of rest is defined as the property of a body to resist any change in its state of rest.

Some examples of inertia of rest are given below.

• To remove the dust particles from a carpet, it is hit with a stick or against a wall.

When the carpet is hit, the carpet moves, but the dust particles remain stationary due to the inertia of rest.

Inertia of motion

Inertia of motion is defined as the property of a body to resist any change to its state of uniform motion.

Some examples of inertia of motion are given below.

• When a fast-moving bus stops abruptly, the passengers fall forward. When a bus driver suddenly hits the brakes, as the bus comes to a stop, the bottom half of the body comes to a stop too, while the upper part of the body continues to move forward because of the inertia of motion. As a result, the body experiences a forward force, and passengers slide forward.
• Luggage transported on a bus is often secured with a rope. This is because luggage placed on the roof of a bus may fall from the roof due to inertia of motion if it is not tied to the bus.

The inertia of direction:

The inertia of direction is defined as a body’s ability to resist changes in its motion direction.

Some examples of inertia of direction are given below.

• Passengers descend towards the center of the curved road when a bus driver takes a bend. When a driver drives through a curve, the passengers feel a force acting away from the curve’s center, which occurs due to the passengers’ tendency to continue going in a straight line.
• A stone is attached to a thread, whirling in a horizontal circle. If the string tears, the stone will fly away in a tangential direction.

Conclusion

The body’s inertia rises as the body’s mass grows, and the converse is true. A force is defined as an object being pushed or pulled. When two items come into contact with each other, they exert a force on each other. Stretch and squeeze are other words that can be used to describe forces. Force is a physical cause that can alter an object’s state of motion or dimensions.