Exam-style question
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Which of the following is the rest energy of a 1 kg mass?.
- A.9 × 10^16 J
- B.1.8 × 10^17 J
- C.4.5 × 10^16 J
- D.3 × 10^16 J
Model answer
What a good answer should say
- 9 × 10^16 J
Explanation
Why this works
Formula: E = m c^2. Substitution: m = 1 kg, c = 3 × 10^8 m/s.
Working: E = 1 × (3 × 10^8)^2 = 9 × 10^16 J. Answer: 9 × 10^16 J.
Units: J. Conclusion: The rest energy of 1 kg is 9 × 10^16 J.
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