What is the science behind a Nail

Anthropomorphically speaking, the Nail observes a Wall in front of it, and a Hammer up its A**e.

Well, if you truly mean "on" the wall rather than "in" it, I assume you're dealing with magnatism or a pretty darned exoctic type of sticky nail and/or wall.

If you mean "in" the wall, then you're dealing with friction, conservation of momentum, etc.

But more importantly if you're male and driving those nails into a wall without the permission of the woman of the house, then odds are you're about to learn an entirely different and painful lesson in physics.

The force on the big head of the nail is transmitted to the small point. The same force over a smaller area gives a greater pressure pushing the nail into the wall.

Say the nail head is 10 mm square and the point is 1mm square. Then the pressure at the ponit is 10 times that at the head.

Apply the same reasoning to a drawing pin (thumb tack) and you will se how it works.

'mm square' or 'square mm', mmmm ? "....when I nod my head, you hit it"

No offense, Del, but I think you are erroneously trying to apply hydraulic theory to a simple transfer of energy, via an object in motion. The size of the nail head really has nothing to do with driving the nail, per se, but functions merely to help keep the nail penetrating in a straight line while being hit with the hammer, and the head helps to retain the material being fastened.

Ok.... I suggest you try reversing the nail and try driving it home

But seriously I do take your point (ooh stop with the puns already)...but there is some truth in what I say, take the thumb tack analogy...you certaily couldn't press it home if it didn't have the big flat head.
Nails are pointed so as to concentrate the enegy over a small area... ok you are right that with a hammer rather than a thumb the head area is only there to protect the hammer face... I'll except I'm wrong at one end, but right at the other.
Probably my head end is right...I blame my arse for any errors

but functions merely to help keep the nail penetrating in a straight line ?????

How come a point helps it go in a straight line?

Del

Yup, the large head on a thumb tack is there only to protect your thumb from impaling itself on the tack, if it didn't have the large head. It takes the same force to drive a given tack (or nail), whether it has a head or not. The point just advances a nail in the direction it is pushed. Have you ever tried to drive a bent nail... the point doesn't go straight into the wood.

Yeh, ok I surrender.

The nail merely transfers the force unchanged from hammer to nail.

The nail is a relatively small diameter purely to save material commensurate with the required strength.
A half inch diameter nail is just as easy to drive a an 1/8" nail...
Oh hang on ...no it isn't.

The smaller the diameter the easier it is to drive because the force is concentrated over a smaller area. (both in terms of cross sectional area and surface area once it's in the wood.

Ever seen 'snow shoes' or 'duck boards' for walking over snow and mud respectively?... they work in the opposite way, e.g they spread the load over a large area, thus reducing the pressure and allowing you to traverse the otherwise hostile surface.

Maybe we should settle for an honourable draw? (or wait for Fyzz?)

Del

Okay... now, I think you've got it. Who woulda thought we'd get this much mileage out of a nail? It's been fun. :-)

"... this much mileage out of a nail ..."

How much mileage could you get out of a nail?

Maybe the topic for a new thread, but ...

Assuming you could get all the energy out of a nail (by finely dividing it & burning it in oxygen, say) - and by comparison with the energy available when petrol (gasoline) is burnt in an engine, how far would that take a Honda 50 with an average (median) weight adult (20 - 40 year old) man?

There's some food for thought! I'm off to find a nice quiet bunker.

BTW - this reminds me of the kind of question my tutor used to chuck at us, about 35 years ago, just to keep us on our toes.

Yuk, yuk, yuk. I suspected when I mentioned mileage someone would jump on it. I'll just bet you often run for the bunker. Cheerio! :-)

Caveat - nuclear reactions not allowed!

Basically, it is friction that must be overcome to drive a nail into a material, and it is friction, once again, that works to hold the nail in the material. A dissertation on nails can be found here...http://books.google.com/books?id=fMZwUGf6wJoC&pg=PA129&lpg=PA129&dq=what+holds+a+nail+in+wood&source=web&ots=xMkLGb-f-i&sig=7U3Suz2H95yUpt-X2WUVONdqpkM&hl=en#PPA129,M1

Driving a nail into wood, there are also wedge effect due to the tip of the nail spreading the wood fibres.

It's easy to split timber with wooden wedged once you have got a split started.

If you start to analyse it you will probably find the maths and science will prove nails don't work .

Stress or shear, or both.