Question-

Mass and Energy

Use the equivalence of energy and rest mass to answer the following questions.

a) How much mass does a 100 W lightbulb dissipate (in heat and light) in one year?

b) The total electrical energy generated in the United States is on the order of 1012 kW · h per year. How much mass is this equivalent to?

c) A student pedaling a bicycle full throttle produces about one-half horsepower of useful power. (1 hp is equivalent to 746 W.) The human body is about 25 percent efficient: 75 percent of the food burned is converted to heat and 25 percent is converted to useful work. How long will the student have to ride to lose one pound by conversion of mass to energy? How come you do not have to exercise this long to lose a pound?

d) The earth's orbital radius is about 1.5 · 1011 m. At this distance from the sun, the energy flux of sunlight is about 1.4 kW/m2. How much mass does the sun radiate as light in one second?