Mechanical-energy conservation and dissipation
Mechanical energy is only part of the total energy.
Key knowledge
For a Newtonian particle under time-independent conservative forces plus other forces, E_mech=K+U and ΔE_mech=W_other. When the other forces do zero work, mechanical energy stays constant. Friction can convert ordered mechanical energy into internal energy; loss of K+U is compatible with total-energy conservation for a correctly chosen combined system.
Values and equations
E_mech=K+U; ΔE_mech=W_other
- E_mech,K,U,W_other
- Mechanical energy, kinetic energy, potential energy and work by forces not represented in U J
Conditions and scope
- Use a fixed inertial frame and a time-independent potential representing the conservative forces.
- A moving/time-dependent potential, deformable body or mass exchange needs additional terms. Choose whether surrounding bodies and internal energy belong to the model before assigning the energy transfer.
Sources · 1
References
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Evidence and review
Read §8.3 Systems with a Single Particle, mechanical-energy balance8.12 and zero-other-work condition8.13; total/internal-energy distinction is the scoped interpretation of dissipation, not an assertion that every subsystem conserves K+U.
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Entry details
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- foundation-physics-mechanical-energy-balance
- Revision
- foundations-refresh.1
- Structured reference record
- Foundational reference additions