> P D Wrote:
> -------------------------------------------------------
> > Dickie Thompson Wrote:
>
> > -------------------------------------------------------
>
> > This is the same as saying 20 pound wheels reach the same top speed as
> 1
>
> > pound wheels right? But the 1 pound wheels accelerates quicker?
>
> I believe you have it right , provided the same amount of energy is
> equally applied , start to finish .
technically, no: the rotating mass has the same effect as static mass on the vehicle. it is intuitive that a heavier vehicle actually takes more *energy* to accelerate to a given speed (and has to dump more energy to slow back down again). the same is true for rotating mass.
the key difference between the two is a measure of magnitude... in the flywheel mass scenario remember that the engine is going from let's say 2k to 10k rpm. now add 1lb to the circumference of a 6" flywheel. at 2k rpm it's moving 37inches*2000 or 74k inches/ minute. at 10k it's 370k inches/ minute, a difference of 296k in/min.
take that same 1lb and just add it to your luggage and it only has to accelerate as much as the vehicle.. 5 mph = 5280 in/min, 40 mph = 42240 in/min, a difference of 37k in/min.
in this hypothetical situation the rotating mass carries an ~8x penalty vs static. in other words, that 1lb on the flywheel is the same as 8lbs in the backpack. both will eventually reach the same top speed on level ground, but the 8lb backpack will require more gas (energy), more distance, and more time to get there.