A spring of constant 400 N/m is stretched by 0.3 m. How much energy is stored in it?
Answer and explanation
Correct answer: B. 18 J
- Step 1: Elastic energy = ½kx². Step 2. E = ½ × 400 × 0.3² = 18 J. Answer: 18 J. Why not the others: 36 J is what you get if you forget the factor ½. 60 J is what you get if you forget to square the extension. 120 J is what you get if you give the force instead.
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