Grade 11 · Physics
Mechanical Energy & Conservation
Why it matters
Kinetic and potential energy.
Core20m readingPrerequisite: Work & Power
What is the conservation of mechanical energy?
Short answer
The conservation of mechanical energy states that when only conservative forces like gravity act, the total mechanical energy — kinetic plus potential — of a system stays constant. Energy converts between kinetic and potential forms, but the sum does not change. Friction and other non-conservative forces transfer some of it to thermal energy, so mechanical energy is then no longer conserved.
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Frequently asked questions
- When is mechanical energy not conserved?
- When non-conservative forces such as friction or air resistance act, they convert some mechanical energy into heat, so the mechanical total drops.
- What are the two forms of mechanical energy?
- Kinetic energy (energy of motion) and potential energy (stored energy, such as gravitational potential energy).