----- Original Message ----- From: "Andy Ross" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, February 28, 2002 5:21 PM Subject: Re: [Flightgear-devel] JSBSim changes
[snip] > > This doesn't hold for the blasphemous "engineering" units. How many > pounds of thrust are required to accelerate an aircraft with a mass of > 3000 pounds by one foot per second per second? I dunno. Trying this > in SI: How many newtons of thrust are required to accelerate an > aircraft with a mass of 1500 kg by one m/s^2? The answer, immediate > and obvious, is 1500. > > To be fair, SI isn't the only system that has this property. There is > another metric system that goes by "cgs" (for centimeter/gram/second > -- the basic units) with the same property. Those folks talk about > force in "dynes" and energy in "ergs". Lets not forget that english units do work well when one stops using pound-mass and uses slugs for mass (1 slug = 32.2 lb-mass). Then no conversion factors are required 1 lb-force = 1 slug * 1 ft/s^2. This makes life much easier and many of us don't mind using slugs (expect for maybe thermo people who just can't seem to get away from lb-mass). Now we know immediately that it takes 300 lbs to accelerate 300 slugs by 1 ft per second per second. Rob _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
