How to explain the spontaneous dynamics that position the tacks, nails or screws to puncture the vehicles tires? When I was a boy, I lived in a city that produced many leather shoes, and because of this our bykes had their tires punctured constantly by tacks thrown in the streets. We know, this happens with the tire of other vehicles besides the bikes.
I'm very intrigued by this magic or revenge of tacks, nails, and screws to those who pass over them. How does this happen?
I have heard that the first tire that passes, lifts the tack that can puncture the second tire.
I'm not sure, but I think front or rear tires was punctured in the same proportion.
 A: The tack will balance point-up if its centre of mass is above the base and it will fall on its side if the centre of mass is outside the base. In both cases, the tack must have insufficient kinetic energy to rotate to the other state.
With a tack, the centre of mass is going to be somewhere along the shaft close to the head.
The energy will be a lot after it has been hit by a car, diminishing as it bounces around.
The chances that the tack lands on its head will depend on the width of the head, the length and weight of the shaft and the evenness of the road and probably a few other things.
If I had to make a rough on-the-spot estimate it would be that the chance of the tack landing head up is proportional to π radians divided by the angle between the shaft and a line drawn from the centre of mass to the edge of the head.
A more accurate result would be gained, however, by going down the hardware store, buying a box of tacks, throwing them up in the air, and counting how many landed point up.
