Exam-style question
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If an object has a rest energy of 1.8 × 10^17 J, what is its mass?.
- A.1 kg
- B.2 kg
- C.3 kg
- D.0.5 kg
Model answer
What a good answer should say
- 2 kg
Explanation
Why this works
Formula: E = m c^2. Substitution: E = 1.8 × 10^17 J, c = 3 × 10^8 m/s.
Working: m = E / c^2 = 1.8 × 10^17 / (9 × 10^16) = 2 kg. Answer: 2 kg.
Units: kg. Conclusion: The mass is 2 kg.
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