In a real pendulum swinging back and forth, the total mechanical energy slowly decreases because
Correct answer: B. energy is transferred to the surroundings as heat and sound by air resistance and friction at the pivot
- A. energy is destroyed
- B. energy is transferred to the surroundings as heat and sound by air resistance and friction at the pivot
- C. gravity weakens
- D. the mass of the bob decreases
Explanation
Energy is conserved overall, but the mechanical energy of the pendulum is gradually converted into thermal energy of the air and the pivot, so the amplitude decays. In an ideal frictionless case the exchange between kinetic and potential energy would continue indefinitely. Nothing is ever destroyed, which is what the conservation principle asserts.
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About Energy Losses and Efficiency
Efficiency compares useful output energy or power with the total input, usually expressed as a percentage. The topic covers energy losses through friction, heating, resistance and sound, along with power ratings and Sankey diagrams. Efficiency is not the same as conservation of energy, because lost energy is transferred rather than destroyed.
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