Brakes G60's vs UFO's and other combos............

Dan Cordon cord4530 at
Tue Feb 17 11:22:48 EST 2004

Bernie Benz wrote:
> Dan, you may wish to rethink your "power logic".  New math, new physics?

Sure....power is the time rate of change of energy. Or, average power is 
energy divided by the time taken for that energy flow to happen.

Slowing a particular car - fast or slow - will require the same amount 
of energy. Unless this happens *really* slow, the majority of this 
energy will end up as thermal energy going in to the brake components.

So, if the same amount of energy is transferred in both circumstances, 
but one happens over a shorter time, then more power occurs in the 
faster time interval.

Look at the flip side......accelerating from 0-60 mph. You must agree 
that more power transferred to the ground will accelerate the vehicle to 
60 mph faster. However, once going 60 mph, the same car will have the 
same kinetic energy - regardless of how fast it got there. F=m*a, and 
conservation of energy works in both directions. Old math, and old physics.

Dan Cordon
Mechanical Engineer
University of Idaho - Engine Research Facility

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