Work and Energy

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Work Noun

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[wurk]

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Work

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The transfer of energy that occurs when a force is applied to an object through a displacement in that force's direction.

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Example: This diagram shows the formula for calculating work (W) using a triangle mnemonic, relating it to force (F) and distance (s).

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System Noun

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[sis-tuhm]

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System

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The specific object or group of objects of interest being studied or analyzed, distinct from the external world.

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Example: In science, a system is the specific part of the universe being studied, separated from its surroundings by a boundary, across which energy can be exchanged.

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Joule (J) Noun

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[jool]

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Joule (J)

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The SI unit of work and energy, defined as the work done by a one-newton force over a one-meter displacement.

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Example: This image shows that no scientific work (measured in Joules) is done on the box because the force holding it up is not in the direction of motion.

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Net Work Noun

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[net wurk]

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Net Work

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The algebraic sum of the work done by all individual forces acting on a system, also known as total work.

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Example: A person pushes a crate with an applied force (Fp) while an opposing force like friction (f) acts against the motion. Net work is the total work done by all forces combined.

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Energy (E) Noun

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[en-er-jee]

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Energy (E)

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The ability of a system to produce a change in itself or the world around it, measured in joules.

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Example: An electric cell (battery) pushes electrons to flow through a conductor (wire), creating electric energy that lights up a bulb.

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Work-Energy Theorem Noun

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[wurk en-er-jee thee-uh-ruhm]

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Work-Energy Theorem

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The principle stating that the net work done on a system results in an equal change in its kinetic energy.

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Example: Positive work, where force and displacement are in the same direction, increases an object's kinetic energy. Negative work, where they are opposite, decreases it.

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Kinetic Energy (KE) Noun

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[ki-net-ik en-er-jee]

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Kinetic Energy (KE)

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The energy an object possesses due to its motion, which is dependent on the object's mass and speed.

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Example: This diagram shows that as an object (a ball) falls, its stored potential energy is converted into the energy of motion, which is kinetic energy.

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Power (P) Noun

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[pou-er]

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Power (P)

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The rate at which work is done or energy is transformed, calculated as work divided by the time interval.

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Example: This image shows the formula for power (P), which is calculated by dividing the work done (W) by the time taken (t).

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Watt (W) Noun

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[wot]

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Watt (W)

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The SI unit of power, equivalent to one joule of energy being transformed or work being done per second.

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Example: This image uses a simple formula and example to define a Watt as a unit of power, showing that 1 watt used for 1 second equals 1 Joule of energy.

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Kilowatt (kW) Noun

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[kil-uh-wot]

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Kilowatt (kW)

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A unit of power equal to 1,000 watts, often used to measure the power output of engines and electrical devices.

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Example: A kilowatt (kW) is a unit of power equal to 1,000 watts. This image shows this relationship and compares it to the power used by common appliances.