Conservation of Energy Equations
Reference from the original Physics I textbook.
- Conservation of Energy Equations
When mechanical energy is conserved: K_i + U_i = K_f + U_f. This requires no net transfer of energy into or out of the chosen mechanical system and no conversion to other forms.
Splitting up :
Adding in Heat Loss:
Adding Work:
With no change or heat loss:
K = kinetic energy (J); U = potential energy (J); U_g and U_s = gravitational and spring potential energy (J); HL = mechanical energy converted to thermal energy (J). W_added and W_lost describe other work entering or leaving the system; do not count the same friction transfer again in both HL and W_lost.
1 joule = 1 N·m = 1 kg·m²/s². Also, 1 newton = 1 kg·m/s².
- Related Glossary Terms
Collision Equations, Conservation of Kinetic Energy Equation, Energy
- Index
Reviewed physics notes (3)
These corrections keep the original lesson’s purpose while fixing errors in the source edition.
- A joule is N·m; N·s is momentum or impulse. — Reference 1
- Mechanical-energy conservation is conditional, unlike conservation of total energy. — Reference 1
- Prevents double-counting dissipation as both work lost and heat loss. — Reference 1
Glossary and deeper reading · 1 refreshers
These editorial refreshers supplement the reading. Definitions and examples are added guidance; original source wording and recorded answers remain in their original context.
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Conservation of energy
Conservation of energy means total energy is unchanged when the full isolated system is considered. Energy can transfer between objects or change form, so one selected energy store need not remain constant. For example, friction can reduce a sliding block’s kinetic energy while increasing the thermal energy of the block and floor.