# Question 7a: ​ On Earth in 2017, the amount of electrical energy used was 8.03 x…

Question 7a: ​ On Earth in 2017, the amount of electrical energy
used was 8.03 x 10​16​ J. How much mass would need to be converted
directly to energy to release this much energy?

Question 7b: ​ Imagine this conversion of mass to energy all came
from nuclear fission reactions of the element uranium. Assume the
reaction is 35% efficient: that means that the mass you calculated
above to produce the electrical energy is only 35% of the total
mass that was converted to energy. The other 65% was “waste”
energy. How much total mass was converted to all kinds of
energy?

Question 7c: ​The amount of mass actually converted to energy is
just a small fraction of the original uranium’s mass: just
0.0000885 of the original mass (0.00885%). Given all these
assumptions, how much total mass of uranium must be available to
create all the electrical energy used in the world, in one year?
(The total reserve of uranium-235 currently available is about
37,000 tonnes, or 3.7 x 10​7​ kg.)