Simple physics question,

[xx44]

but I suck in physics so that's why I will let you answer.

Is it easier to break 3 1" boards with one blow of a fist, sledge hammer, etc... if they are placed directly on top of one another, or if they are stacked with a 1" gap between each of them?

[gull]

I vote gapped.

I'm not sure if the physics behind it is so simple though.

[daryn]

what is creating this gap?

[TomTom]

Let’s assume the boards are the typical karate boards, which to me look like 1 by 12 boards, very wide, and they are split across the width. Wood doesn’t have much bend in this direction and will snap apart easily with the grain; this is why karate people break boards like this. They are exploiting an inherent weakness in the wood by breaking it with the grain.

So… if you place the boards in contact you must exert enough force to break all 3 at the same time.

The spacers used are narrow slices of the same boards placed along the board edges parallel to the grain. What they do is allow each board freedom of movement.

If you have them spaced an inch apart each will be broken in turn one after the other, and the force to break each one is about a third of that to break them at the same time. As each board begins to bend it snaps (before touching the next board or this analysis doesn’t apply). Once snapped in half it no longer impedes the hand/hammer impacting the boards and thus allows the next board to be freely broken, and so on.

This is why when you see a karate man breaking multiple boards he’ll always have spacers just like this.

[superadvisor]

Let’s assume the boards are the typical karate boards, which to me look like 1 by 12 boards, very wide, and they are split across the width. Wood doesn’t have much bend in this direction and will snap apart easily with the grain; this is why karate people break boards like this. They are exploiting an inherent weakness in the wood by breaking it with the grain.

So… if you place the boards in contact you must exert enough force to break all 3 at the same time.

The spacers used are narrow slices of the same boards placed along the board edges parallel to the grain. What they do is allow each board freedom of movement.

If you have them spaced an inch apart each will be broken in turn one after the other, and the force to break each one is about a third of that to break them at the same time. As each board begins to bend it snaps (before touching the next board or this analysis doesn’t apply). Once snapped in half it no longer impedes the hand/hammer impacting the boards and thus allows the next board to be freely broken, and so on.

This is why when you see a karate man breaking multiple boards he’ll always have spacers just like this.

[superadvisor]

Damn, beat me to it [img]/images/graemlins/frown.gif[/img]