Newton’s Laws of Motion

Newton's Laws of Motion

When a book is kept on the table, is anything happening there? `It's just stationary' you'd answer. And you're right! But even in this stationary mode, the book is exerting a type of gravitational force towards the earth. Confused? Well, this is one of the applications of Newton's first law of motion. But what are laws of motion? Let us study in-depth below.

What is Force?

`Force' is a vector quantity that can be described as a push or pull on an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, the objects experience an equal and opposing force on each other. In other words both the objects `exert force' on each other. Force only exists as a result of an interaction. If there is no interaction, the objects no longer experience the force.

Force is measured in units called Newtons (N), named after the famous scientist Sir Issac Newton. This force further divides into:

a. Balanced Forces b. Unbalanced Forces

Balanced Forces

When an object is not moving with changing speed i.e. it's in equilibrium, the net force acting on it is `balanced'. For example, the weight of the apple is balanced by the force exerted by the branch on the apple, when an apple hangs from a tree.

Unbalanced Forces

When an object is not in equilibrium i.e. moving with changing speed, the net force on it is `unbalanced'. For example, when an apple falls

from the tree an unbalanced force equal to its weight is acting on the apple.

What are the different types of Forces?

What is Inertia?

The tendency of a body in motion continues to remain in motion, moving with uniform velocity and a body at rest continues to remain at rest unless acted upon by a force. This tendency of the body is known as `inertia' (i.e. resistance to change). In Newton's First Law of Motion, this concept is quantified. The word inertia comes from the Latin word `iners', that means idle or lazy.

Inertia is a quality, all the objects/bodies in nature made of matter that possess. Mass is a measure of inertia. Objects with higher mass resist changes in motion more than objects with lower mass.

What is Newton's Universal Law of Gravitation?

Laws of Motion

Sir Isaac Newton worked in many areas of mathematics and physics. He developed various theories of gravitation when he was only 23

years old. In around 1698, some twenty years later he presented the three laws of motion. Newton's laws of motion give us the relations between the forces acting on a body and the motion of the body.

These laws are as follows:

Newton's First Law of Motion also known as Law of Inertia states that every object persists to stay in uniform motion in a straight line or in the state of rest unless an external force acts upon it.

Newton's Second Law of Motion states that force is equal to the change in momentum per change in time. For a constant mass, force equals mass times acceleration, i.e. F = m*a. Learn about the Acceleration in detail here.

Newton's Third Law of Motion states that for every action there is an equal and opposite reaction.

Derivation of Newton's Second Law of Motion

According to Newton's second law:

F

 =d P /dt , where P = momentum and P =m

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