# Scientists Say: Joule

This unit is a measure of energy or work

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**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.