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An engine burns 1.4 kg of gasoline per hour and yields 3.5 kW of power. Calculate the efficiency of the engine when the heating value of gasoline is 43 MJ/kg.

  • 3 years ago
  • 3 years ago

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  1. BecomeMyFan=D
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    i dont even know where to start

    • 3 years ago
  2. BecomeMyFan=D
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    ANY help, even a formula or a rule or a hint, anything will help

    • 3 years ago
  3. BecomeMyFan=D
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    i just know efficiency = input/output

    • 3 years ago
  4. lokisan
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    Yep, calm down.,,

    • 3 years ago
  5. BecomeMyFan=D
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    oh, sorry, it is output/input

    • 3 years ago
  6. BecomeMyFan=D
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    ok,.... i am calm

    • 3 years ago
  7. lokisan
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    The heating value is the amount of heat energy produced by complete combustion in a given quantity. Take a basis of 1 hour. Then your engine burns 1.4kg of gasoline, which yields a maximal amount of thermal energy to use for work as\[43MJ/kg \times 1.4 kg=60.2MJ\]In one hour, your engine produces from this energy, \[\frac{3500J}{s}\times \frac{3600s}{h}=12.6MJ\]The efficiency is the amount of work per unit energy input, which is \[\eta = \frac{12.6MJ}{60.2MJ}=0.209\]to 3 significant figures.

    • 3 years ago
  8. lokisan
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    This is the first time I've used 'heating value' for anything like this, so if the answer's wrong, I couldn't find an appropriate definition.

    • 3 years ago
  9. BecomeMyFan=D
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    so, can i say that efficiancy is 20.9%?

    • 3 years ago
  10. lokisan
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    Yes

    • 3 years ago
  11. BecomeMyFan=D
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    ok, thank you, i already faned you long time ago, so cant fan again :(

    • 3 years ago
  12. lokisan
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    Yeah I know - no worries :)

    • 3 years ago
  13. lokisan
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    The answer makes sense - I've seen values between 10 and 50% for internal combustion engines.

    • 3 years ago
  14. BecomeMyFan=D
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    then it is probably correct, i also know that cobustion engines are very unefficient

    • 3 years ago
  15. BecomeMyFan=D
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    hey anwar

    • 3 years ago
  16. AnwarA
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    hi :)

    • 3 years ago
  17. BecomeMyFan=D
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    want a fan?

    • 3 years ago
  18. AnwarA
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    would you be one if I say yes?

    • 3 years ago
  19. BecomeMyFan=D
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    ...

    • 3 years ago
  20. AnwarA
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    lol

    • 3 years ago
  21. BecomeMyFan=D
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    you got it

    • 3 years ago
  22. AnwarA
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    thanks!!

    • 3 years ago
  23. BecomeMyFan=D
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    anwar, can you please fan lokisan, because he helped me alot and i can only fan him once

    • 3 years ago
  24. AnwarA
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    lol you really care about others :P.. I already did anyways

    • 3 years ago
  25. AnwarA
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    so you faned me just as an exchange for me to fan the guy huh? :(

    • 3 years ago
  26. BecomeMyFan=D
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    nah, would have faned you anyway

    • 3 years ago
  27. sstarica
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    lol andy, you and your fanning job~ ^_^

    • 3 years ago
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