werkenergie

Werkenergie, or "work energy" in Dutch, is a fundamental concept in classical mechanics that describes the relationship between the work done on a body and the energy it gains or loses, with emphasis on kinetic energy.

The central statement is the work-energy theorem: the net work done on a particle equals the change in its kinetic energy. In mathematical terms, W_net = ΔK = (1/2) m v^2 − (1/2) m v0^2, where m is mass, v is final velocity and v0 is initial velocity. Work is defined as the line integral of force along the displacement, W = ∫ F · ds.

If only conservative forces act, the work converts between kinetic and potential energy, so the total mechanical energy E = K + U remains constant. When non-conservative forces (such as friction) perform work, mechanical energy is transformed into other forms like heat or sound, and E is not conserved in the mechanical sense, though total energy (including internal energy) is conserved.

The concept extends to systems of particles and to more advanced regimes. In relativity, the kinetic energy is γmc^2 − mc^2 and the work–energy relation reflects the work done by forces in accelerating a particle. In practice, werkenergie provides a practical framework for analyzing motion, braking, energy transfer in machines, and energy recovery systems, connecting forces, motion, and energy in a coherent account of dynamics.