May 16, 2022

Newton’s Laws of Motion: Definition, Elements, and Examples

netwon's laws

At some point in their lives, people will certainly get familiar with Newton’s Laws of Motion, a set of concepts that were first introduced by one of the most famous physicists of all time, Sir Isaac Newton. In Indonesian curricula, Newton’s Laws of Motion are first introduced to students in junior high schools. From there, students gradually learn more about the laws as they continue their education.

In the study of physics, this subject is very important as it’s based on real everyday life. Moreover, the laws are broken down into formulas that are useful to solve physics problems related to the motion of objects. In the article, we’ll briefly talk about the definition, elements, and examples of Sir Isaac Newton’s Laws of Motion.

The Definition

To start our discussion, it’s important to note that Newton’s Laws of Motion consist of three different laws; each of them is closely related to a common term in everyday physics: a force. A force is an influence that can change the motion of an object; it can be measured through certain formulas. The three laws, which were formulated by Sir Isaac Newton, are about force.

Newton’s Laws of Motion explain the relationship between a physical object and the forces acting upon it and are represented by three formulas. The formulas are known as Newton’s First, Second, and Third Laws. Because of his noble contribution to the world, Newton was honored with the title Sir.

The Laws

newton's laws

Newton’s First Law: Inertia

Newton’s first law states that an object at rest will remain at rest, and an object in motion will remain in motion at a constant speed and in a straight line unless acted upon by a force. This law is known as the law of inertia.

Newton’s Second Law: Force

Newton’s second law is basically a quantitative description of the changes that a force can create in the motion of an object. It states that the acceleration of an object depends on the mass of the object and the amount of force applied. The acceleration will be proportional to the amount of force acting on the object but will be inversely proportional to the mass of the object.

Newton’s Third Law: Action and Reaction

Newton’s third law states that when two objects interact, they apply forces to one another that are equal in magnitude and opposite in direction. The third law is also known as the law of action and reaction.

Also read: Capillarity: Definition, Formula, and Examples

The Formulas

Newton’s First Law: Inertia

∑F = 0

∑F is the amount of all forces

Newton’s Second Law: Force

F = ma

F = Force (N)

m = mass (kg)

a = acceleration (m/s2)

Newton’s Third Law: Action and Reaction

F action = F reaction

There are three implementations of Newton’s Third Law, which lead to three formulas.


Ffriction =   µN

Ffriction = Friction (N)

µ = coefficient of friction

N = normal force


W = mg

W = Weight (N)

m = mass (kg)

g = gravitational acceleration (m/s2)

Specific Weight

γ = ρ g

γ = Specific weight (N/m3)

ρ = density (kg/m3)

g = gravitational acceleration (N)

Elements of Newton’s Laws of Motion


A force is a push or a pull upon an object resulting from the object’s interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. In the MKS metric system, force is measured in Newton; in the cgs metric system, it’s measured in dyne.

Speed and Velocity

In physics, speed and velocity are two different terms. Speed is the time rate at which an object is moving along a path, while velocity is the rate and direction of an object’s movement. Put another way, speed is a scalar value, while velocity is a vector. They also have different formulas.

Mass and Weight

In physics, mass and weight are also different. The difference between mass and weight is that mass is the amount of matter in a material, while weight is a measure of how the force of gravity acts upon that mass.

Examples in Real Life

Newton’s First Law: Inertia

Imagine driving a car fast. If you suddenly step on the brake pedal, the car passenger behind will automatically be pushed forward. In contrast, imagine driving slowly. If you suddenly step on the accelerator pedal, the passengers will be pushed backward.

Newton’s Second Law: Force

Imagine throwing a rock vertically up to the sky. The rock will initially travel at a constant speed but then slow down and stop due to the earth’s gravity. After that, the rock will descend to the surface at the speed determined by the mass of the rock and the force of gravity.

We’ve arrived at the end of our discussion on Newton’s Laws of Motion. Physics is fun, right? If you’re interested in Physics and looking for a school that have great Physics lessons, join Sampoerna Academy, an international school powered by the Cambridge curriculum and the pioneer of the STEAM learning approach in Indonesia. For more information about Sampoerna Academy, visit here!

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