The total U.S. consumption of electricity in a particular year was 5.0 x 1012 kilowatt-hours. What is the mass equivalence of this amount of energy? Show all calculations leading to an answer.
E = m c^2
c is about 3*10^8 meters/second
5*10^12 kw h (10^3 w/kw)(3600 s/h)
= 1.4 * 10^12 watt seconds which is JOULES
so
m = 1.4*10^12/(9*10^16)
= .156 * 10^-4
= 1.56 * 10^-5 kilograms
= 1.56 * 10^-2 grams
= .00156 grams
which is why nuc bombs are scary