In rec.aviation.piloting Montblack wrote:
wrote)
In cars, weight matters most in acceleration and doesn't matter in any
significant amount with modern tires in cruise.


Speculate please:

1. Two 3,600 lb cars - good tires
2. Traveling 60 mph (no wind)
3. 4cly - 150 hp (Honda Accords)
3. Flat highway in North Dakota
4. Fuel flow meters hooked up to both vehicles

(Honda #1)
Driver ................ 105 lbs
Fuel .................... 15 lbs
TOTAL .............. 120 lbs (1/30th of 3,600 lb car)

(Honda #2)
Driver ................. 300 lbs
Passengers ........ 700 lbs
Luggage ............. 100 lbs
Fuel ................... 100 lbs
TOTAL ............. 1,200 lbs (1/3 of 3,600 lb car) ....BTW, BTDT! g

If both vehicles were monitored for 50 miles, would their fuel flow be
(approx) the same, in cruise?

A pulled out of my ass, wild assed guess is that since you are
increasing the load by 33%, then yes, you will see a difference,
and at that loading the tires will be visibly deformed.

Now, would you care to calculate the energy required to accelerate
3720 pounds to 60 mph versus accelerating 4800 pounds to 60 mph?

Assume gasoline is 45 megajoules per kilogram and the engine is 38%
efficient.

You may neglect all drag for this calculation and express the energy
in kilograms of gasoline.



--
Jim Pennino

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