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wrong assumption
Posted by Siegfried (more from Siegfried) on Thu, 14 Jun 2012 19:17:51
In Reply to: Another way of looking at this, Reality, Thu, 14 Jun 2012 13:20:13
Reality,
your assumption that breaking is a process if transferring kinetic energy into energy required to disjoin brake pads and rotors atoms is incorrect. Breaks dissipate kinetic energy into heat and its their inefficiency factor of how much of that energy goes into material destruction (disjoining atoms).

Consider the pads being not of frictional type, but magnetics. And the rotors being made of aluminum (or copper, silver and so forth). In this case there will be no (zero) material loss in the pads and rotors while braking and all the energy will transform into a pure heat. It's the Eddy currents which do that trick (courtesy of mr. Foucault... well, and the Lord as well).

It's like you were saying 'it takes 10 minutes of 200W grinder to wear the tires into the same condition which they have after 20K miles of run - so why do we need to spend all the energy from gasoline required to make those 20K miles the conventional way?'. A perfect tire has no wear, but nothing under the mood is perfect and it's the level of inefficiency which turns into wear. It isn't about amount of energy those things have dealt with: two tires having the same wear may have a way too different mileages between each of them.

Zig

posted by 87.228.10...
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