(J) The SI unit of work or energy.
Definition: The work done by a force of 1 newton acting to move an object through a distance of 1 meter in the direction in which the force is applied.
Since kinetic energy is one half the mass times the square of the velocity, 1 joule is the kinetic energy of a mass of two kilograms moving at a velocity of 1 m/sec.
The joule is named for the British physicist James P. Joule.

Ability to do work, measured in joules (J).

An MKS unit of energy expended over time or of angular momentum.
Definition: 1 planck is equal to 1 joule second (J * s) or about 0.7375 foot pound second (ft * lb * s).
Atomic nuclei possess an intrinsic angular momentum referred to as spin, measured in multiples of Planck's constant. The unit is named for the German physicist Max Planck.

(V) The SI unit of electric potential.
Definition: The amount of potential energy present per unit of charge. 1 volt representing a potential of 1 joule per coulomb of charge.
The unit is named for the Italian scientist Count Alessandro Volta.

(W) The SI unit of power.
Definition: 1 watt is equal to a power rate of one joule of work per second of time or in electrical terms it is the power produced by a current of one ampere flowing through an electric potential of one volt.
Power is the rate at which work is done, or the rate at which energy is expended and is used both in mechanics and in electricity.
The unit is named for James Watt, a British engineer.