Elastic strain energy Quiz
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5 questions, one answer each
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1. A spring has stiffness 400 N m⁻¹ and is stretched by 0.10 m. What is the elastic strain energy stored?
- A. 2.0 J
- B. 4.0 J
- C. 20 J
- D. 40 J
2. What does the area under a force-extension graph represent?
- A. The stiffness
- B. The work done, stored as elastic strain energy
- C. The extension
- D. The Young modulus
3. A student uses ½Fx for a rubber band whose force-extension graph is curved. What is wrong?
- A. The extension must be doubled
- B. Energy is not stored in rubber
- C. ½Fx applies only if the force is proportional to extension
- D. The force must be squared
4. A spring is stretched from 0.10 m to 0.20 m. Which expression gives the extra energy stored?
- A. ½k(0.10)²
- B. ½k(0.20 − 0.10)²
- C. ½k(0.20)²
- D. ½k(0.20)² − ½k(0.10)²
5. A spring launcher stores 0.75 J and fires a ball with 0.53 J of kinetic energy. What is the efficiency?
- A. 70%
- B. 30%
- C. 140%
- D. 0.53%