Question

Most of us have some sense of how we benefit individually or
as a society, from the consumption of energy. We are also aware of the fact that energy comes to
us from a variety of sources, and that energy can be transported and stored in several ways. We
also hear about the downsides of using non-renewable resources, of being “addicted to oil,” and
of serious environmental effects from producing and consuming fossil fuels.
Consider a standard U.S. 55-gallon drum of diesel fuel. Using the information below,
calculate how long a fit, healthy human worker must perform hard physical labor, to produce the
work output that can be obtained from a drum of diesel fuel. State your answer in time units that
make the comparison easy to understand.
 “A healthy well-fed laborer over the course of an 8-hour work shift can sustain an
average output of [up to] about 75 watts.” (Wikipedia – Human Power)
 1 horsepower = 745.7 watts.
 Maximum diesel engine efficiency ≈ 50%
 Standard U.S. work week = 40 hours
 Typical U.S. work year = 50 weeks
 1 liter = 1,000 cm 3 = 0.264 U.S. gallon
 Diesel fuel heating value = 43.4 MJ/kg (1 MegaJoule = 10 6 Joules)
 Diesel fuel density = 0.832 grams/cubic centimeter
 1 watt = 1 Joule/second

Answer 1

this means that if a laborer works for 7 works years almost , he/she will be able to match the energy of diesel fuel.

Or 6 years 48weeks and 9 minutes approximately.