Work and Energy Lecture Review

Flashcards covering key vocabulary and concepts from the 'Work and Energy' lecture, including definitions of energy forms, work, power, and types of forces.

Energy Conservation

A fundamental principle stating that energy can neither be created nor destroyed.

Kinetic Energy

Energy that describes motion and relates to an object's mass and its velocity squared. Formally, KE = ½ mv².

Potential Energy

Energy stored in an object due to its position (height and mass) or through elastic deformation (e.g., in a spring).

Energy Dissipation

The process by which energy is transferred at the molecular level, often as heat and noise, and becomes unavailable for work.

Work

The product of a constant force (F) through a parallel displacement (s). W = F ⋅ s = (F cos θ)s. It is a scalar quantity.

Joule (J)

The SI unit of Work and energy. One Joule is equal to one Newton-meter (N·m).

Erg

The CGS unit of Work, equivalent to dyne-centimeter (dyn·cm).

Positive Work

Work done by a force when its component points in the same direction as the object's displacement (θ between 0° and 90°, cos θ > 0).

Negative Work

Work done by a force when its component points in the direction opposite to the object's displacement (θ between 90° and 270°, cos θ < 0).

Zero Work

Work done by a force when it is perpendicular to the direction of displacement (θ = 90°, cos θ = 0).

Work-Energy Theorem

States that when a net external force does work on an object, the kinetic energy of the object changes according to Wtotal = ΔKE = KEf - KE_o.

Elastic Potential Energy (U_elastic)

Energy stored in a spring due to being stretched or compressed by an amount x from its unstrained length. U_elastic = ½ kx², where k is the spring constant.

Gravitational Potential Energy (U_grav)

The energy an object of mass m has by virtue of its position relative to the Earth's surface, measured by its height h; U_grav = mgh.

Conservative Force

A force for which the work done on a moving object is independent of the path taken between the object's initial and final positions, and does no work on an object moving around a closed path. Examples: gravitational, elastic spring, electric forces.

Nonconservative Force

A force for which the work done on a moving object depends on the path taken. The work it does on an object moving around a closed path is not zero. Examples: static and kinetic frictional force, air resistance, tension.

Total Mechanical Energy (E)

The sum of the kinetic energy (K) and potential energy (U) of an object (E = K + U).

Conservation of Mechanical Energy

If the net work done on an object by nonconservative forces is zero, then its total mechanical energy (E = K + U) remains constant.

Average Power

The rate at which work is done, calculated by dividing the work by the time required to perform it. P = W/Δt.

Watt (W)

The SI unit of power, equal to one Joule per second (J/s).

Instantaneous Power

The power at a specific moment, given by the product of the force and the instantaneous velocity in the direction of the force. P = Fv.