The Physics
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Opus in profectus

# Work

## Summary

• Work defined
• Work is done whenever a force results in a displacement.

W = Fs

The component of the force parallel to the displacement (F) is what matters.
• Work is the scalar product of force and displacement.

W = Fs cos θ

• Work is the force-displacement path integral. W = ⌠⌡ F · ds
• Work-energy theorem
• Work is done when the energy of an object changes form (energy transduction).
• Work is done when energy is transfered from one system to another (energy transfer).
• Work is a change in energy.
 W = ∆E
 F∆s cos θ = ∆E
calculus version
 ⌠⌡ F · ds = ∆E

• Units
• The SI unit of work and energy is the joule, named after the English physicist and brewer James Joule (1818–1889).

[J = N m = kg m2/s2]

• The electronvolt is an acceptable non SI unit of energy. It is used for some applications in electromagnetism; solid state, atomic, nuclear, and particle physics; and related sciences like biophysics, chemistry, and astronomy. An electron volt is the work done a particle with one elementary charge when it is moved between two points with a potential difference of one volt. It is described in more detail in the section on electric potential (a.k.a. voltage).

1 eV = (1.6 × 10−16 C)(1 V) = 1.6 × 10−16 J