Classifying Work and Energy

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Work Noun

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[wurk]

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Work

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A change in a system's state caused by a force applied along a displacement, transferring energy to or from the system.

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Example: This diagram shows the formula for calculating work (W) using force (F) and distance (s), and how to rearrange it to find any variable.

Front

Displacement Noun

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[dis-pleys-muhnt]

Back

Displacement

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The change in an object's position, defined as a vector quantity with both magnitude and direction from start to end.

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Example: A basketball moves from a higher initial position to a lower final position. This change in position is its displacement.

Front

Joule (J) Noun

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[jool]

Back

Joule (J)

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The standard international (SI) unit of work and energy, equivalent to one newton of force applied over one meter.

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Example: The image shows how a Joule, the unit of energy, is calculated by multiplying power (in Watts) by time (in seconds).

Front

Positive Work Noun

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[poz-i-tiv wurk]

Back

Positive Work

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Work done on a system when the applied force has a component in the same direction as the displacement, increasing energy.

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Example: This image shows positive work because the person applies a force (push) on the object, and the object moves in the same direction as the force.

Front

Negative Work Noun

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[neg-uh-tiv wurk]

Back

Negative Work

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Work done on a system when the applied force has a component in the opposite direction of the displacement, decreasing energy.

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Example: This diagram shows negative work occurs when the net force on an object is in the opposite direction of its displacement, causing it to slow down.

Front

Zero Work Noun

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[zeer-oh wurk]

Back

Zero Work

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The condition where no energy is transferred, occurring when force is perpendicular to displacement or there is no displacement.

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Example: When two people pull a rope with equal and opposite force, the rope does not move. Since no work is done without displacement, this is zero work.

Front

Pressure Noun

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[presh-er]

Back

Pressure

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The amount of force exerted perpendicularly on a surface, measured as a scalar quantity of force per unit of area.

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Example: This image shows that atmospheric pressure is higher at lower altitudes because there is more air above, creating more weight (force) pushing down.

Front

Isobaric Process Noun

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[ahy-soh-bar-ik pro-ses]

Back

Isobaric Process

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A thermodynamic process in which the pressure of a system remains constant while its volume changes, resulting in work being done.

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Example: Heating a gas in a container with a movable piston causes it to expand. Because the weight on the piston is constant, the pressure remains the same.

Front

Energy Noun

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[en-er-jee]

Back

Energy

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A quantitative property of a system that enables it to perform work, associated with motion and the position of particles.

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Example: This diagram shows that a ball held at a height has stored potential energy, which transforms into kinetic energy (the energy of motion) as it falls.

Front

Kinetic Energy Noun

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

Back

Kinetic Energy

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The energy an object possesses due to its motion, which is dependent on its mass and the square of its velocity.

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Example: A moving car has kinetic energy because it possesses both mass and speed; the amount of energy depends on these two factors.