Planes, Trains and Automobiles Answers

Actually, I think the smoke is a bad thing. As you point out it means the tyres are skidding as they spin up to match the speed of the aircraft. In the process some of the aircraft’s kinetic energy is converted into heat, noise and tyre ablation. I would say that a negligible amount of kinetic energy is transferred from the body of the plane to the spinning wheels. If these wheels didn’t have brakes, then yes, the conversion of kinetic energy into heat through friction with the tarmac would cease when the wheels got up to speed.

But these wheels have brakes. The amount of force that the aircraft can place on the tarmac to counter its kinetic energy is considerably greater when the tyres are in contact with the tarmac and not skidding and ablating than when they are (static vs dynamic friction). The brakes, then, are the bits that skid and ablate, but now we have a brake disc skidding against a brake pad – two objects engineered to be able to apply a *lot* of friction to each other and convert that kinetic energy into heat energy. Far more energy can be expended by the sliding brake discs than can be expended by the sliding tyres.

This is why we have anti-lock brakes and why engineers have looked for ways to start spinning aircraft wheels before they hit the tarmac, because you can’t slow the aircraft down until the wheels grip – all that smoke is just so much burnt rubber.