The law of conservation of energy states that energy
Correct answer: C. can be transformed from one form to another but the total remains constant
- A. can be created when needed
- B. can be destroyed by friction
- C. can be transformed from one form to another but the total remains constant
- D. always increases in an isolated system
Explanation
Friction does not destroy energy; it converts organised kinetic energy into disordered thermal energy, which is harder to use but is still energy. Every apparent loss in mechanics is a transfer to a form outside the system being considered. Including mass as a form of energy through E equals mc squared makes the law hold in nuclear reactions too.
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About Work-Energy Theorem
The work-energy theorem states that the net work done on an object equals its change in kinetic energy. Questions involve positive and negative work, variable forces and force-displacement graphs, acceleration or deceleration, and the difference between this theorem and conservation of mechanical energy, which also requires attention to potential energy and non-conservative work.
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