Work (w)

Definition

Work (W) is the energy transferred to or from an object via a force acting over a distance. It is measured in joules (J) and calculated as the product of force and displacement in the direction of the force.

5 Must Know Facts For Your Next Test

1. The formula for work is $W = F \cdot d \cdot \cos(\theta)$, where $F$ is force, $d$ is displacement, and $\theta$ is the angle between the force and displacement vectors.
2. Work can be positive or negative depending on the direction of the force relative to the displacement.
3. In thermochemistry, work often refers to pressure-volume work done by or on gases, calculated as $W = -P \Delta V$, where $P$ is pressure and $\Delta V$ is change in volume.
4. When a gas expands against constant external pressure, it performs work on its surroundings.
5. Work done on or by a system contributes to changes in its internal energy according to the first law of thermodynamics.

Review Questions

• What is the equation used to calculate work when a constant force acts along a straight path?
• How does pressure-volume work differ from other types of mechanical work?
• What role does work play in the first law of thermodynamics?

Related terms

Energy: The capacity to do work or transfer heat. It exists in various forms such as kinetic, potential, thermal, and chemical.

First Law of Thermodynamics: States that energy cannot be created or destroyed, only transferred or converted from one form to another. Mathematically expressed as $\Delta U = Q + W$, where $\Delta U$ is change in internal energy, $Q$ is heat added to the system, and $W$ is work done on the system.

Heat (Q): A form of energy transfer between bodies due to temperature difference. Unlike work, heat transfer occurs spontaneously from higher temperature objects to lower temperature ones.