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In the world of physics, Sir Isaac Newton is the pioneer of classical physics with his laws of motion. The first law of Newton is also called the law of inertia. The law of inertia is the most important and recognized. In this article, let us discuss the first law of inertia in detail. Before we discuss the law of inertia, let us know the definition of inertia. Inertia is the property of matter due to which it remains at the state of rest or in uniform motion in the same straight line unless an external force acts on it.
Introduction
Inertia is the resistance of a physical body/object to a change in its velocity. This includes the changes to the object’s speed, or in the direction of motion of the body. One aspect of this property is the tendency of objects to move in a straight line at constant speed when no force is acting on them.
The amount of inertia which is possessed by an object is proportional to its mass. But the inertia is not the same as the mass or momentum (product of the velocity and mass). The mass of an object may be measured by noticing the extent of its inertia. This is done by determining the amount of force needed to produce a certain acceleration .
Law of Inertia
Law of inertia is the Newton’s first law of motion. According to the law of inertia if a body is at rest or moving at a constant velocity in a straight line then the body will remain at rest or keep moving in a straight line at the constant speed unless an external force acts on it. Before Galileo, it was assumed that all horizontal motion required a direct cause, but Galileo concluded from his experiments that a body in motion would remain in motion unless a force (like friction) would bring it to a standstill.
Galileo’s Free Fall Experiment
The most accepted theory of motion in Western philosophy before the Renaissance, was the Aristotelian theory according to which “In the lack of external power, every objects would return to rest that moving objects only continue to move as long as there is a power inducing them to do so.” Despite its general acceptance, the Aristotelian theory was rejected by many philosophers. Later, Galileo redefined the theory of inertia.
Classification of Inertia
Classification of inertia are as mentioned
Inertia of rest | Inertia related to direction | Inertia of motion |
Until and unless an external force is applied, the body is in the position of rest. | The capability of the body to move in the same direction of motion until a force is applied on the body, is known as inertia of direction. | The position of a body, where the body exhibits uniform motion until an external force acts on it, it is known as Inertia of motion. |
Moment of Inertia
The moment of inertia is defined as the quantity expressed by the body resisting angular acceleration, which is the sum of the product of the mass of each particle and the square of it’s distance from the axis of rotation of an object. Or, more simply put, it can be described as a quantity that determines the amount of torque required for a given angular acceleration on an axis of rotation. The SI unit is kg.m2
The moment of inertia is
I=mr2
Here,
m = Summation of product of the mass.
r = distance.
I = Moment of Inertia.
Inertia & Mass
According to the Newton’s Second Law “the force acted on an object is always equals to the product of mass and acceleration of that object.”
Hence the force is
F=ma
Here,
F = force
m = mass
a = acceleration
Examples of Inertia
Basic example of inertia is when the train suddenly starts to move in the opposite direction while we are facing towards the other direction, it seems that the lower body part gets a motion whereas the upper part remains at rest.
For the game of high jump, an exact distance is covered by the sportsmen through running.
A person sitting inside a car and the brakes are applied suddenly, the person ahead.
Examples of the Law of Inertia
The law of Inertia comes into existence when the lift starts suddenly.
- When a lift suddenly operated, we experienced a jerk.
- When a driver applied the brake suddenly, we moved forward.
Conclusion
In the world of physics, Sir Isaac Newton is the pioneer of classical physics with his laws of motion. The first law of Newton is also called the law of inertia. The law of inertia is the most important and recognized. In this article, let us discuss the first law of inertia in detail. Before we discuss the law of inertia, let us know the definition of inertia. Inertia is the property of matter due to which it remains at the state of rest or in uniform motion in the same straight line unless an external force acts on it.
There are mainly three types of inertia
Inertia of rest
Inertia of direction
Inertia of motion
The most accepted theory of motion in Western philosophy before the Renaissance, was the Aristotelian theory according to which “In the absence of external power, every objects would return to rest that moving objects only continue to move as long as there is a power inducing them to do so.” Despite its general acceptance, the Aristotelian theory was rejected by many philosophers. Later, Galileo redefined the theory of inertia.
Example
Brakes applied by bus driver suddenly
On a bus trip, when the bus driver suddenly presses the brake, we tend to feel a momentary push forward. The reason for this feeling by passengers sitting inside the bus is because of the law of inertia. Due to the inertia of motion, our body continues to maintain a state of motion even after the bus has stopped, thus pushing us forward.
Newton’s Second Law of Motion
Sir Isaac Newton’s First Law of Motion states, A frame at relaxation will continue to be at relaxation, and a frame in movement will be in movement until it’s far acted upon via any outer or external force. Then, what occurs to a frame while an outside force is carried out to it? That scenario is defined by Newton’s Second Law of Motion. According to NASA, this regulation states, Force is identical to the change in momentum in line with change in time. For a regular mass, force equals mass into acceleration. In mathematical form it is written as F = ma, where F equals force, m is mass of object and a is acceleration of object. The math at the back of that is pretty simple. If you double the force, you double the acceleration, however in case you double the mass, you narrow the acceleration in half. Because the acceleration is directly, and mass is inversely proportional.
Formula
According to Newton’s Second laws of motion
F = ma
Where, F = force, m = mass of the object, a = acceleration
Example
Hitting of a ball
A ball develops a certain acceleration after being hitted. The acceleration with which the ball moves is directly proportional to the force acting on it. This means the harder you will hit the ball, the faster it will move, proving Newton’s second law in everyday life.
Newton’s Third Law of Motion
According to Newton, whenever objects A and B interact, they exert force on each other. When you sit in the chair, your body exerts a downward force on the chair, and the chair exerts an upward force on your body. Here are two forces resulting from this interaction: a force on the chair and a force on your body. These two forces are called action force and reaction force and are the subject of Newton’s third law of motion. Basically it stated by Newton’s third law is: for every action, there is an equal and opposite reaction. The statement means that in every interaction there is a pair of forces acting on the two interacting objects. The size of the forces on the first object is equal to the size of the force on the second object. And the direction of the force on the first object is opposite to the direction of the force on the second object. Forces always occur in pairs of equal and opposite reaction-action forces.
Example
Stretching an elastic band
When someone pulls an elastic band, it returns to its authentic position automatically after leaving it. The more distance you pull it, it exerts the extra force. This is identical while you pull or compress a spring respectively. This pull action is stored as energy and is released as a reaction with the same and opposite force.
Conclusion
Newton’s give three important laws of motion that become the root of classical mechanics, it explains every aspect related to rest and motion of any object. Moreover it explains about the force acting on the object and it also explains that every object exerts forces on each other when they are in contact.
