Physics Exam 3: Work, Energy, and Thermodynamics

Vocabulary flashcards covering core physics definitions, laws, equations, and conversion standards across classical mechanics, work and energy, harmonic motion, and thermodynamics.

Work

The transfer of energy resulting from a force causing an object to move through a displacement ($W = F \times d$); the application of force alone without motion does not constitute work.

Joule ($\text{J}$)

The standard SI unit for both work and energy, equivalent to a Newton-meter ($\text{N}\cdot\text{m}$).

Watt ($\text{W}$)

The SI unit of power, defined as one Joule per second ($1\,\text{J/s}$) or work performed per unit time ($\frac{W}{t}$).

Kinetic Energy ($\text{KE}$)

The scalar form of energy possessed by a moving object due to its mass and velocity, defined mathematically as $\text{KE} = \frac{1}{2}mv^2$.

Power ($P$)

A measure of the rate at which an engine or system can perform work, calculated as $P = \frac{W}{t}$.

Work-Energy Theorem

The principle stating that the total work done on an object by all forces equals its change in kinetic energy ($W = \Delta \text{KE} = \text{KE}_{\text{final}} - \text{KE}_{\text{initial}}$).

Negative Work

Work done by a force acting in the direction opposite to an object's displacement—such as kinetic friction acting on a sliding body—which reduces the body's mechanical energy.

Gravitational Potential Energy ($\text{GPE}$)

The energy stored in an object due to its vertical height in a gravitational field, given by the formula $\text{GPE} = mgh$.

Elastic Potential Energy ($\text{EPE}$)

The potential energy stored in an elastic spring of force constant $k$ when it is stretched or compressed by a distance $x$, equal to $\frac{1}{2}kx^2$.

Vertical Spring-Mass Displacement

The mechanical process in which pulling a suspended mass downward through a height $h$ decreases its gravitational potential energy ($\text{GPE}$) while increasing the elastic potential energy ($\text{EPE}$) stored in the stretched spring.

Simple Harmonic Motion ($\text{SHM}$)

A periodic oscillatory motion exhibited by systems like pendulums and springs, driven by a restoring force directed toward the center that increases proportionally with distance away from the center.

Absolute Zero

The lowest possible temperature a body can approach ($0\,\text{K}$, $-273.15^\circ\text{C}$, or $-459.67^\circ\text{F}$), at which fundamental particles have minimal vibrational motion and an ideal gas exerts zero pressure or volume.

Temperature Scales Comparison

The relationship among thermal scales where water freezes at $273\,\text{K} = 0^\circ\text{C} = 32^\circ\text{F}$, normal human body temperature is $310\,\text{K} = 37^\circ\text{C} = 98.6^\circ\text{F}$, and water boils at $373\,\text{K} = 100^\circ\text{C} = 212^\circ\text{F}$.

Ideal Gas Law

The thermodynamic equation of state expressed as $PV = nKT$, establishing that at constant pressure the volume of a fixed mass of gas is directly proportional to absolute temperature, and at constant volume pressure is directly proportional to temperature.

Heat ($Q$)

Thermal energy transferred from one body to another solely as the result of a difference in temperature, flowing spontaneously from the hotter body to the cooler body.

Thermal Conduction

The transfer of thermal energy through matter to adjacent matter via direct physical contact, occurring without the flow or bulk mixing of the material itself.

Thermal Convection

The mechanism of heat transfer through fluids (liquids and gases) via the bulk displacement and mixing of fluid clumps, caused naturally by density differences or artificially by fans and pumps.

Thermal Radiation

The mode of heat transfer occurring via electromagnetic waves (such as infrared, light, or ultraviolet) emitted by a hot body and absorbed by a cooler body, requiring no medium.

Thermal Conductivity

The material property characterizing the rate at which heat conducts through a substance; conductors such as metals have higher thermal conductivities than thermal insulators such as wood.

Specific Heat Capacity ($c$)

The quantity of heat energy required per unit mass to raise the temperature of a substance by one degree, defined by the formula $c = \frac{Q}{m\Delta T}$.

Latent Heat of Fusion ($L_f$)

The amount of heat required to change a unit mass of a substance from solid to liquid at its melting point without an increase in temperature; for ice, $L_f = 80\,\text{cal/g}$.

Latent Heat of Vaporization ($L_v$)

The amount of heat required to convert a unit mass of a substance from liquid to vapor at its boiling point at constant temperature; for water at $100^\circ\text{C}$, it equals approximately $540\,\text{cal/g}$.

First Law of Thermodynamics

The statement of the principle of conservation of energy applied to thermodynamic systems: $\Delta U = Q - W$, where the change in internal energy equals net heat transferred into the system minus net work done by the system.

Kilowatt-Hour ($\text{kWh}$)

A unit of electrical energy consumption equal to power multiplied by time ($\text{power} \times \text{time}$).

Calorie ($\text{cal}$)

A non-SI metric unit of thermal energy where $1\,\text{cal} \approx 4.16\,\text{J}$ to $4.18\,\text{J}$, and $1\,\text{kcal} = 1000\,\text{cal}$.