>Lets say you are pulling a trailer behind that car, with big heavy
>15" steel wheels. Are you suggesting that the vehicle will do as
>much work to create rotational motion in those wheels as it does to create
>rotational motion in the drive wheels?
Sure, assuming the wheels are the same size/weight/etc. Disregarding
wheelspin, all the wheels have to be rotationally (and linearly, of course)
accelerated at the same rate, subject to the formula for rotational
acceleration. Where do you suppose the force is coming from if not the
engine?
>Is that work greater than the work required to move the weight of the
>trailer?
Maybe, maybe not. Depends on the mass of the trailer, eh?
>If not, then would this analogy apply to the non-drive wheels on the
>vehicle?
Sure.
>Work transmitted through the drive wheels creates motion. The drive
>wheels have to be turned for the motion to take place, therefore the
>engine not only moves the vehicle but also turns the wheels. This is
>where the rotational mass becomes an issue. Free wheels are not directly
>turned by the engine, they simply assist in easing the work requirement of
>the drive wheels.
What you're calling "free" wheels also have to be turned for the motion to
take place, again disregarding wheelspin. The car can't move forward
without rotationally accelerating ALL of the wheels, right?
Where you're getting tangled up is defining your system. If you define the
system as being exclusively the drivetrain and drive wheels, then yes, the
other axle is outside that system and needn't be accounted for. However,
that's not a very useful way of looking at things since in most successful
racing endeavors the entire car has to complete the race, not just the
drivetrain. Disregarding wheelspin, the drive and non-drive wheels have to
accelerate rotationally and linearly at exactly the same rate. The only
impetus in the system to perform that work is the engine. If you don't want
to disregard wheelspin, then you still have to account for the acceleration
of the non-driven wheels, but the acceleration rate of the driven wheels
will be greater, and therefore yes, lighter wheels will be more of an
"advantage". The quotes are there because again in most successful racing
endeavors wheelspin isn't necessarily desirable.
KeS
>Time to hit the books.
Ayuh.
KeS
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