Physics Lecture: Conservation of Energy and Nonconservative Forces

Vocabulary flashcards covering conservative and nonconservative forces, energy equations, and work principles discussed in the physics lecture.

Conservative Force

A force that stores energy as potential energy where the work done is independent of the path or configuration taken, such as gravity or restorative spring forces.

Nonconservative Force

A force for which the work done depends on the path taken or configuration, acting to either add energy to a system (such as a push) or remove mechanical energy from it (such as friction or air resistance).

Conservation of Mechanical Energy

The principle stating that the initial potential energy plus initial kinetic energy equals the final potential energy plus final kinetic energy ($PE_i + KE_i = PE_f + KE_f$) in a system where only conservative forces do work.

Gravitational Potential Energy

The stored energy an object possesses due to its position or height above the ground, given by the expression $mgh$.

Spring Potential Energy

The potential energy stored in a spring when it is compressed or stretched by a displacement $x$, calculated using the formula $\frac{1}{2}kx^2$.

Frictional Force

The primary nonconservative force that opposes motion, doing path-dependent work that removes kinetic energy from a system and converts it into heat, sound, or material deformation.

Impact Force

A nonconservative force occurring when an object collides with a surface or barrier, absorbing energy from the colliding object and transferring it into sound, heat, or deformation.

Work-Energy Theorem

The theorem defining net work ($W_{\text{net}}$) as the sum of all conservative and nonconservative work done on an object, which equals the object's change in kinetic energy ($\Delta KE$).

Mechanical Work Equation

The mathematical formula $W = Fd\cos(\theta)$, where $F$ is the applied force, $d$ is the displacement distance, and $\theta$ is the angle between the direction of the force and the direction of displacement.

Conservation of Energy with Nonconservative Work

The formulation stating that the initial kinetic energy plus initial potential energy plus nonconservative work equals the final kinetic energy plus final potential energy ($KE_i + PE_i + W_{\text{nc}} = KE_f + PE_f$).

Braking Force (Car Example)

The nonconservative retarding force with a scalar magnitude of $2{,}660\,\text{N}$ (vector force of $-2{,}660\,\text{N}$) needed to bring an $850\,\text{kg}$ car traveling at $25\,\text{m/s}$ ($90\,\text{km/h}$) to rest over $100\,\text{m}$.

Full Law of Conservation of Energy

The comprehensive principle stating that total initial energy equals total final energy across all forms, expressed as $KE_i + PE_i + W_{\text{nc}} + E_{\text{other}, i} = KE_f + PE_f + E_{\text{other}, f}$, incorporating thermal, sound, electrical, and nuclear energies.