Scientists Say: Joule

This unit is a measure of energy or work

apple picking

Lifting this small apple one meter from the ground will require about one joule of work.

Linda Hartley/Flickr/(CC BY 2.0)

Joule (noun, “JOOL”)

This is a unit used to measure energy or work. One joule is the amount of energy required to produce one watt of power for one second. It’s also the work done by a force equal to one newton exerted over a distance of one meter.

It’s named after James Prescott Joule. He was a 19th century physicist who determined that energy is never destroyed. It’s just converted from one form to another. 

In a sentence

One joule is about the energy required to lift a single 100 gram apple one meter off the ground.

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Power Words

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joule  The amount of energy needed to produce one watt for one second. Joule is a standard unit of energy.

newton  A unit of force named for Sir Isaac Newton, a 17th century English physicist and mathematician. One newton is an amount that would give a mass of one kilogram an acceleration of one meter per second per second.

watt    A measure of the rate of energy use, flux (or flow) or production. It is equivalent to one joule per second. It describes the rate of energy converted from one form to another — or moved — per unit of time. For instance, a kilowatt is 1,000 watts, and household energy use is typically measured and quantified in terms of kilowatt-hours, or the number of kilowatts used per hour.

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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