If 7.84 × 107 J of energy is released from a fusion reaction, what amount of mass in kilograms would be lost? Recall that c = 3 × 108 m/s.

This requires use of that well known equation E = mc^{2}

Rearrange to get m = E/c^{2}

m=7.84*10^{7}/(3*10^{8})^{2 } kg = (7.84/9)*10^{-9} kg. ≈ 8.7*10^{-10} kg

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