Question

How much amount of energy is liberated in converting $1\, kg$ of coal into energy?

• A. $9 \times 10^{16} J$
• B. $9 \times 10^{15} J$
• C. $3 \times 10^{14} J$
• D. $4 \times 10^{6} J$

Answer 1

Answer: (A)

According to mass-energy equivalence,
$E=m c^{2}=1 \times\left(3 \times 10^{8}\right)^{2}$
$=9 \times 10^{16} J$
So, $9 \times 10^{16} J$ of energy is liberated in converting $1\, kg$ of coal into energy.