Work, Energy, and Power Lecture Notes

A set of vocabulary flashcards covering the definitions, units, and formulas of work, energy, and power as presented in the lecture.

Work ($W$)

The product of the force exerted on an object and the displacement the object moves in the direction of the force ($W = F \cdot d$).

Joule ($J$)

The SI unit of work and energy; the work done when $1.0\,N$ of force is applied through a distance of $1.0\,m$.

Work Formula (with Angle)

The equation used when force and displacement are not in the same direction: $W = Fd(\cos(q))$, where $q$ is the angle between force and displacement.

Energy

The ability or capacity to do work; it is a scalar quantity that comes in forms such as mechanical, electrical, thermal, and chemical.

Kinetic Energy ($KE$)

The energy of motion possessed by moving objects with mass, calculated as $KE = \frac{1}{2}mv^2$.

Potential Energy ($PE$)

Stored energy or the energy an object has due to its position or condition.

Gravitational Potential Energy ($PE_g$)

Energy of position calculated using the formula $PE_g = mgh$, where $g$ is the acceleration of gravity ($9.8\,m/s^2$) and $h$ is height.

Elastic Potential Energy ($PE_e$)

Energy of condition stored in elastic materials, calculated as $PE_e = \frac{1}{2}kx^2$, where $k$ is the elastic constant and $x$ is elongation or compression.

Law of Conservation of Energy

The principle stating that energy can be neither created nor destroyed, but may only change forms.

Work-Energy Theorem

The principle stating that the net work done on an object is equal to its change in kinetic energy ($W_{net} = \Delta KE$).

Power ($P$)

The time rate of doing work or the time rate of transferring energy ($P = \frac{W}{t}$).

Watt ($W$)

The SI unit of power achieved when $1.0\,J$ of work is done or $1.0\,J$ of energy is transferred in a time of $1.0\,s$.

Horsepower

A unit of power based on a work-horse's average output, where $1\,\text{Horsepower} = 750\,\text{Watts}$.

calorie (cal)

The amount of heat energy required to raise the temperature of $1.0\,gram$ of water by $1^\circ\text{C}$; equivalent to $4.184\,J$.

Calorie (Food Calorie)

A unit equal to $1000\,calories$ or $1\,kcal$, equivalent to $4184\,J$ or $4.18 \times 10^3\,J$.

Kilowatt-hour ($kW\text{-}hr$)

A unit of energy equal to $10^3\,W \times 3600\,s$, which results in $3.6 \times 10^6\,J$.