Using Einstein's relation, the energy released when a mass defect of 2 kg is fully converted (c = 3 x 10^8 m/s) is
A1.8 x 10^17 J
B6.0 x 10^8 J
C1.8 x 10^9 J
D9.0 x 10^16 J
Answer & Solution
Correct answer: A. 1.8 x 10^17 J
1. Use Einstein mass-energy relation $E = mc^2$.
2. List the data: $m = 2\,\text{kg}$ and $c = 3\times10^{8}\,\text{m/s}$.
3. Square the speed of light: $c^2 = (3\times10^{8})^2 = 9\times10^{16}$.
4. Multiply by the mass: $E = 2 \times 9\times10^{16}$.
5. So $E = 1.8\times10^{17}\,\text{J}$.
6. Trap D forgets to multiply by the mass; traps B and C forget to square c.
_Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 6 Nuclear Physics "Nuclear Physics", p.92_
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