Newton vs. Joule: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on March 3, 2024
Newton is a unit of force in the International System of Units (SI), while Joule is the SI unit of energy, highlighting their roles in physics as measures of force and energy respectively.

Key Differences

A Newton (N) is defined as the force required to accelerate a one-kilogram mass at a rate of one meter per second squared. It quantifies the magnitude of force applied to an object, fundamental in the study of mechanics and dynamics. On the other hand, a Joule (J) measures the amount of work done when a force of one Newton displaces an object by one meter in the direction of the force. This distinction places Joules at the heart of energy transfer and work done in physics, bridging concepts like potential and kinetic energy.
Newtons are used to express forces including weight (due to gravity), tension, and friction, Joules are employed to quantify various forms of energy, such as mechanical, thermal, and electrical. This reflects their foundational roles in distinct but related physical principles: forces causing movement and the capacity to do work or produce heat.
The relationship between Newtons and Joules is further illustrated in the work-energy principle, where the work done on an object (in Joules) is the product of the force applied (in Newtons) and the distance over which it is applied. This connection underscores the interdependence of force and energy in describing physical phenomena.
The conversion between Newtons and Joules involves the distance moved; without specifying distance, one cannot directly convert Newtons to Joules or vice versa. This highlights their conceptual difference: force as an interaction that changes the motion of objects versus energy as a measure of work done or stored.
Despite their differences, both Newtons and Joules are crucial for understanding the physical world. They enable precise descriptions of the forces that govern motion and the energy transformations that underlie all physical processes, from the microscopic to the cosmic scale.

Comparison Chart

Unit of force
Unit of energy

Measurement

Force required to accelerate 1 kg mass by 1 m/s²
Energy transferred when a 1 N force is applied over 1 meter

Force
Energy and work

Application

Describing weight, tension, friction
Quantifying mechanical, thermal, electrical energy

Relationship

Directly relates to acceleration
Represents work done or energy transferred

Newton and Joule Definitions

Newton

Essential for understanding frictional forces.
A box sliding on a surface experiences a frictional force opposing its motion.

Joule

Measures electrical energy.
A 1 watt device consumes 1 J of electrical energy per second.

Newton

Unit of force in the SI system.
A gravity force of 10 N is acting on a 1 kg object near the Earth's surface.

Joule

SI unit of energy.
Lifting a 1 kg object 1 meter high requires about 9.8 J of energy.

Newton

Used to describe weight as a force.
An object's weight on Earth might be 9.8 N/kg due to gravity.

Joule

Integral for understanding kinetic energy.
A moving object with a mass of 2 kg and velocity of 3 m/s has 9 J of kinetic energy.

Newton

Fundamental in calculating tension.
The tension in a cable supporting a 10 N weight is 10 N.

Joule

Used to calculate potential energy.
A 2 kg object held 2 meters above the ground has 39.2 J of gravitational potential energy.

Newton

Measures the amount of force applied.
Pulling a rope with a force of 5 N moves an object.

Joule

Quantifies work done or heat transferred.
Pushing a box 5 meters with a force of 10 N uses 50 J of energy.

Newton

The SI-derived unit of force required to accelerate a mass of one kilogram one meter per second per second, equal to 100,000 dynes. See Table at measurement.

Joule

The International System unit of electrical, mechanical, and thermal energy, equal to the work done when a force of one newton acts through a distance of one meter, and also equal to the work done when a current of one ampere is passed through a resistance of one ohm for one second.

Newton

In the International System of Units, the derived unit of force; the force required to accelerate a mass of one kilogram by one metre per second per second. Symbol: N.

Joule

In the International System of Units, the derived unit of energy, work and heat; the work required to exert a force of one newton for a distance of one metre. Equivalent to one watt of power for a duration of one second. Symbol: J

Newton

English mathematician and physicist; remembered for developing the calculus and for his law of gravitation and his three laws of motion (1642-1727)

Joule

A unit of work which is equal to 107 ergs (the unit of work in the C. G. S. system of units), and is equivalent to one watt-second, the energy expended in one second by an electric current of one ampere in a resistance of one ohm; also called the absolute joule. It is abbreviated J or j. The international joule is slightly larger, being 1.000167 times the absolute joule. The absolute joule is approximately equal to 0.737562 foot pounds, 0.239006 gram-calories (small calories), and 3.72506 x 10-7 horsepower-hours, and 0.000948451 B.t.u.

Newton

A unit of force equal to the force that imparts an acceleration of 1 m/sec/sec to a mass of 1 kilogram; equal to 100,000 dynes

Joule

A unit of electrical energy equal to the work done when a current of one ampere passes through a resistance of one ohm for one second

Joule

English physicist who established the mechanical theory of heat and discovered the first law of thermodynamics (1818-1889)

FAQs

What is a Newton?

A Newton (N) is the SI unit of force, representing the force needed to accelerate 1 kilogram of mass at 1 meter per second squared.

Who was the Joule unit named after?

The Joule is named after James Prescott Joule, an English physicist known for his work on energy and heat.

Who was the Newton unit named after?

The Newton is named after Sir Isaac Newton, an English mathematician, physicist, and astronomer.

What is the formula involving Newtons for force?

The formula is F = ma, where F is force in Newtons, m is mass in kilograms, and a is acceleration in meters per second squared.

What is a Joule?

A Joule (J) is the SI unit of energy, defined as the energy transferred when applying a force of one Newton over a distance of one meter.

Is a Newton a large unit of force?

No, a Newton is a relatively small unit of force; for example, the gravitational force on a small apple on Earth is about 1 Newton.

How are Newtons and Joules related?

They are related through work and energy: applying a force of one Newton over a distance of one meter transfers one Joule of energy.

What applications use the Newton?

Newtons are used in physics and engineering to quantify forces, including weight, friction, and tension.

What is the formula for calculating Joules in terms of work?

The work formula is W = Fd, where W is work in Joules, F is force in Newtons, and d is distance in meters.

What applications use the Joule?

Joules measure energy in various contexts, including electrical, mechanical, and thermal energy.

Can you convert Newtons to Joules?

Direct conversion isn't possible since they measure different quantities (force vs. energy), but they are related through the equation of work done.

How does gravity relate to Newtons?

Earth's gravity exerts a force of 9.8 Newtons on every kilogram of mass, a fundamental concept in calculating weight.

What is the significance of Newton's laws of motion?

Newton's laws describe the relationship between a body and the forces acting upon it, foundational to classical mechanics.

Is a Joule a large unit of energy?

A Joule is a relatively small unit of energy; for example, lifting a small apple 1 meter high requires about 1 Joule of energy.

What is a common misconception about Newtons and Joules?

A common misconception is that they can be directly converted like units of the same quantity, but they measure different physical concepts.

How does electrical energy relate to Joules?

Electrical energy consumption and production are often measured in Joules or kilowatt-hours, where 1 kWh equals 3.6 million Joules.

Can Joules measure thermal energy?

Yes, Joules can measure the amount of thermal energy transferred or produced in thermal processes.

How do Joules apply to everyday energy use?

Everyday energy use, from lighting a bulb to charging a phone, involves transferring energy measured in Joules.

What did James Prescott Joule's experiments demonstrate?

Joule's experiments demonstrated the conservation of energy, particularly how mechanical energy is converted into heat.

How do Newtons apply to everyday phenomena?

Everyday forces, such as pushing a shopping cart or pulling a rope, can be measured in Newtons to quantify the force applied.