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How many miles could the car go with that energy?

  1. Apr 21, 2008 #1
    1. The problem statement, all variables and given/known data
    Suppose one gallon of gasoline produces 1.1 x 10^8 J of energy, and this energy is sufficient to operate a car for twenty miles. If a 362 mg drop of gasoline could be converted completely into thermal energy, how many miles could the car go with that energy?

    2. Relevant equations
    I cannot find a conversion for 1 gallon of gasoline to kilograms. Is it even necessary?? Also, for the 362 mg drop. I know they need to be in kilograms in order for the energy to be in JOULES.

    3. The attempt at a solution
    I used the equation E0=mc^2. I plugged in 1.1 x 10^8 J for the energy and I didn't know what to use for the mass but I know that once I do that I can use the value for C using the same equation, except the second time the mass would be for the 362 mg drop.
    Last edited by a moderator: Jan 7, 2014
  2. jcsd
  3. Apr 21, 2008 #2
    To convert gallons of gasoline to kilograms, you need to know the density of gasoline.

    This problem has nothing to do with relativity. Don't use E=mc^2. Think about how a car engine works.
  4. Apr 21, 2008 #3
    It DOES has to do with relativity because E0=mc^2 is the hint that the website (for this HW problem) gave to solve for the problem. It may not be the bulk of the problem but it is at least partially part of the process.
    Also, how can i relate this problem to how a car engine works?
  5. Apr 21, 2008 #4

    Doc Al

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    Staff: Mentor

    You are told how much energy is sufficient to operate a car for twenty miles; Calculate the rest energy of that drop of gas and compare.
  6. Apr 21, 2008 #5
    I see. I misunderstood. I assumed they wanted an answer to a realistic problem. Ignore what I wrote before.
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