AP Physics: Work, Energy, and Power

This set of vocabulary flashcards covers concepts from Unit 6, including Power, Work, Energy Conservation, and Conservative vs. Non-conservative forces based on the lecture notes.

Power ($P$)

The average rate at which work is being done, or the change in energy over time ($P = \frac{\Delta E}{t}$). It is a scalar quantity.

Watt ($W$)

The SI unit of power, equivalent to Joules per second ($J/s$).

Horsepower ($hp$)

A larger unit of power frequently used for specifying power generated by motors and internal combustion; $1\,hp = 550\,foot\,pounds/second$ or approximately $745.7\,W$.

Principle of Law of Conservation of Energy

Energy cannot be created nor destroyed, but only can be converted from one form to another.

Efficiency

A measure of how much energy is successfully converted; for example, if efficiency is $50\%$, an object may only reach half of its theoretical height ($800\,m$ instead of $1600\,m$).

Work done by a Variable Force

Calculated by dividing the displacement into small segments ($\Delta s$) and finding the area under the force-displacement graph ($W = \text{Area}$).

Conservative Force

A force that is path independent, meaning the work done depends only on the final and initial positions of the object. Examples include gravitational force, elastic force, and electric force.

Non-conservative Force

A force that is path dependent. Examples include friction, tension, and applied forces (push/pull).

Mechanical Energy ($E$)

The sum of kinetic energy ($KE$) and potential energy ($PE$); $E = KE + PE$. It remains constant throughout a path if non-conservative forces are zero.

Principle of Conservation of Mechanical Energy

The total mechanical energy remains constant ($E = E_0$) when all non-conservative forces ($W_{nc}$) acting on the object are zero.

Work ($W$)

A scalar quantity involving a force ($F$) and a displacement ($s$). It is calculated as $W = F \cos(\theta) s$.

Work-Energy Theorem

States that when a net external force does work on an object, the kinetic energy changes from its initial value to its final value ($W = \Delta KE$).

Gravitational Potential Energy ($PE$)

The energy an object possesses by virtue of its position relative to the Earth, measured as $PE = mgh$. It is a conservative form of energy.

Kinetic Energy ($KE$)

The energy an object possesses due to being in motion, calculated as $KE = \frac{1}{2}mv^2$.