How the tube of a tire(cycle) get puncture? I mean, the inner tube is protected by an outer tube, so how is it possible to make a hole in the inner tube? And in general the puncture hole is very small. Why?
When a nail is driven into a tire, it is safe to assume that it happens in the first contact. The reason for this assumption is that the surface of the tire is compliant (bouncy like a spring) so as soon as contact has been made and the nail is lodged in the thread, if no puncture exists, repeatedly pushing on the nail will not make any progress, rather it will push against the compliant surface of the tire (which makes a "tent" around the nail") with no energy being transfered to the tire (no puncture). The part of the nail that sticks out will simply be polished flush over time against the surface of the thread. Remember that pushing on an elastic object (like a spring) causes energy to be absorbed by the spring, only to be released once the force is relieved. And energy would have be spent in the puncture. Also, the hardness of the tire is unlikely to suddenly be reduced to allow the nail to penetrate in a subsequent rotation. Finally, the force driving the nail can be assumed to be about the same on each rotation (a fraction of the car's weight, as distributed according to its dimensions, acceleration rate and grade of pavement, all of these are parameters that change slowly from one tire rotation to another during normal driving, and can be assumed to be about the same)