I am not sure that I agree that energy consumption could be measured in newtons - newtons are a unit of measure of **force**, not a generic shorthand for J/m. There is already a precedent for this type of situartion within SI - the sievert and the gray. A gray (Gy) is a measure of absorbed dose of electromagnetic radiation and a sievert (Sv) is a dose equivalent of electromagnetic radiation. Both are dimensionally equivalent to J/kg. They are related to each other by a "quality factor" which is a function of the type of radiation etc.
_____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of J. Ward Sent: 11 July 2008 04:12 To: U.S. Metric Association Subject: [USMA:41391] the SI unit for automobile energy consumption is the NEWTON Automobile energy consumption is meaningfully expressed as energy/distance. In SI units, that would be J/m, which simplifies to newtons. While probably not of great practical value, it is the SI unit, and it is intuitive. It is equivalent to the force that would be pushing your car if the fuel your car used had been converted perfectly into mechanical energy. For example, on my last tank I managed to coax 40.2 mpg out of my Corolla. That works out to: 40.2 miles = 64 700 m 1 gallon of unleaded gasoline = 131 MJ Thus, I averaged 131 000 000 / 64 700 = 2 025 N. Since most people don't have a good feel for Newtons, on earth that's the weight of 206 kg, which seems rather hefty. To keep it simple, the conversion factor would be: Energy consumption (in Newtons) = 81 300 / fuel economy in MPG My wife's car averages about 3,700 N, which is the weight of 380 kg! Those who prefer distance/energy would use inverse newtons instead of newtons. Not as intuitive. If, on the other hand, we care more about the volume of fuel used rather than energy, then: 1 gallon of gasoline = 0.003785411784 meters cubed 40.2 miles = 64 700 m Thus, my fuel consumption was 0.003785411784 / 64 700 = 0.0586 mm squared, which seems like an amazingly thin thread of gasoline. Would someone check over my reckoning to make sure I haven't made a mistake? J.
