Originally Posted By: canuckInOR
Quite simply, if you forget (or never knew in the first place) that a plane's engine doesn't power the wheels to make it move, you're going to be stumped.

You're also going to be stumped if you forget (or never knew) that the friction forces on the wheels don't increase as the wheels' speed increases -- which is a whole lot less intuitive, IMO.

The dialogue "Does the plane take off?" -- "No" -- "Yes it does" is, in a way, a very roundabout version of the dialogue "Is there a factor for relative speed in the equations of friction?" -- "Yes" -- "No there isn't".

Peter