Definition check – what is energy? Select the most accurate definition used in engineering mechanics for “energy”.
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Apower of doing work
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Bcapacity for doing work
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Crate of doing work
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Dall the above
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Ework per unit time
Answer
Correct Answer: capacity for doing work
Explanation
Introduction / Context:Clear verbal definitions help prevent mix-ups between fundamental quantities: work, energy, and power. Energy underpins analyses of machines, structures, and thermodynamic systems, representing the budget from which mechanical, thermal, or electrical outputs can be produced.
Given Data / Assumptions:
- Classical mechanics conventions for work, energy, and power.
- Scalar quantities unless otherwise stated (e.g., potential, kinetic energies).
- Steady units: Joule for work/energy; Watt for power.
Concept / Approach:
Energy is the capacity for doing work. Work is the energy transfer via a force acting through a distance. Power is the time rate of doing work. The accepted textbook phrasing distinguishes these three succinctly and avoids ambiguity in problem solving and unit checks.
Step-by-Step Solution:
Recall: Work W = ∫ F · ds, unit Joule.Energy E (e.g., kinetic 1/2 m v^2, potential m g h) represents the stored capacity to perform work, unit Joule.Power P = dW/dt, unit Watt = Joule/second.Therefore the correct definition is “capacity for doing work”.Verification / Alternative check:
Dimensionally, energy and work share the same unit; power differs by per-time. Common engineering references adopt precisely this wording.
Why Other Options Are Wrong:
(a) “power of doing work” is vague and conflates with power. (c) and (e) explicitly define power, not energy. (d) cannot be correct because (a), (c), and (e) are not definitions of energy.
Common Pitfalls:
Using “power” and “energy” interchangeably; forgetting that energy is a state property whereas power is a rate.
Final Answer:
capacity for doing work