Physics A.3 Work, Energy and Power

Term: Conservation of energy

Definition: The principle of conservation of energy states that the total energy of an isolated system remains constant, though it may change forms. Energy can neither be created nor destroyed, only transferred or transformed.

Term: Work

Definition: Work is the transfer of energy that occurs when a force is applied to an object and the object is displaced in the direction of the force. It is given by W = Fs cos(θ), where F is the force, s is the displacement, and θ is the angle between the force and displacement vectors.

Term: Sankey diagram

Definition: A Sankey diagram is a graphical representation of energy flows within a system, showing the magnitudes of energy transfers and transformations between different forms of energy.

Term: Mechanical energy

Definition: Mechanical energy is the sum of an object’s kinetic energy and potential energy. It includes kinetic energy (Ek = 0.5mv²), gravitational potential energy (ΔEp = mgh), and elastic potential energy (EH = 0.5kx²).

Term: Power

Definition: Power is the rate at which work is done or energy is transferred. It is given by P = ΔW/Δt = Fv, where ΔW is the change in work, Δt is the change in time, F is the force, and v is the velocity.

Term: Efficiency

Definition: Efficiency is a measure of how effectively a system converts input energy into useful output energy. It is given by η = Eoutput / Einput = Poutput / Pinput, where Eoutput and Poutput are the output energy and power, respectively, and Einput and Pinput are the input energy and power, respectively.

Term: Energy density

Definition: Energy density is the amount of energy stored in a given system or region of space per unit volume. It is typically measured in joules per cubic meter (J/m³).