työenergian

Työenergian (work energy) is a central concept in classical mechanics. In Finnish usage, the term työenergia refers to the relationship between the work done on a body and the change in its energy. The work-energy perspective emphasizes that forces acting on a system alter its energy by performing work as the system moves.

Work is defined as the energy transferred by a force along the path of motion. For a particle of mass m moving a displacement ds under force F, the infinitesimal work is dW = F · ds, and the total work is W = ∫ F · ds over the path.

The work-energy theorem states that the total work done on a particle equals the change in its kinetic energy: W = ΔK = 1/2 m v^2(final) − 1/2 m v^2(initial).

For conservative forces, such as gravity or spring forces, the work is also equal to the negative change in potential energy: W_conservative = −ΔU, and the mechanical energy E = K + U remains constant in the absence of non-conservative forces.

Non-conservative forces, such as friction or air resistance, can change mechanical energy by transferring energy to other forms, often heat. In that case, the work done by non-conservative forces equals the change in kinetic energy, while the total energy (including thermal energy) is conserved.

Applications of the work-energy viewpoint include analyzing motion when forces are known but accelerations are difficult to compute, and in problem solving across physics and engineering. Related concepts include kinetic energy, potential energy, and conservation of energy.