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.

Since E = mc² where E is energy, m is mass and c is the speed of light we have

 

m = 7.84x10⁷/(3x10⁸)² kg  = 7.84x10⁷/9x10¹⁶ kg = 0.871x10^-9 kg = 8.71x10^-10 kg

 

.