1) It has been established that a person can perform continuous manual labor at

Question

1) It has been established that a person can perform continuous manual labor at a power of 50 watts for an 8-hour working day. How many pounds of coal contain the energy equivalent of the useful physical labor a person can perform in this time period? How many gallons of oil?

2) An inventor claims to have developed a wonderful new heat engine that operates with a relatively cool (and therefore nonpolluting) flame at 150°C and discharges waste heat to the environment at 20°C. His promotional literature advertises that 45% of the fuel energy is converted into useful work. Calculate the maximum efficiency that can be expected for such an engine and compare it to the inventor's claim.

Explanation / Answer

power= 50 w

time= 8 hours= 8(3660 s)=28800 seconds

energy needed= power * time=50(28800)=1440000 j

now calorific value of coal (bituminous)= 23250000 j/kg

so amount of coal required= 1440000/23250000

mass of coal= 0.062 kg.

calorific value of gas oil=38000000j/kg

mass oil gas oil required= 1440000/38000000

mass of gas oil=0.038 kg.

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.