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I'm doing a school assignment project and I need to investigate something of my choice. I was thinking of doing something about how the height and angle the blade of a guillotine is dropped from affects how accurately and/or how deep it cuts. And also, it wouldn't hurt if anyone knew the directions to building a mini guillotine. So does anyone know the basic Physics of the guillotine, per se? There's not much about it on the internet and I might have to go and search the library for more info... But if anyone could help, I'd soo appreciate it! thanks all!

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closed as off topic by Qmechanic, Ron Maimon, David Z May 23 '12 at 15:33

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This is not a good project for school, the physics is trivial and the topic is morbid. –  Ron Maimon May 22 '12 at 20:49
I disagree with Ron, this could be a fine topic for your project (as long as your teacher is not squeamish :-P). But it's not an appropriate question for this site. We handle conceptual physics questions here, it's not an idea farm. –  David Z May 23 '12 at 15:36
@Ron M - I really dont think it's morbid but on the subject of triviality, could you expand a bit? thanks. –  Jesus-mothic-chick May 27 '12 at 19:28

1 Answer 1

up vote 2 down vote accepted

Meh, morbidity and triviality aside, the basic principle of a guillotine is: Lots of momentum behind a sharp edge produces cutting. An angled blade increases the efficiency of the cut by maintaining higher pressure at the cutting interface than if the entire blade made contact at once.

In building one, you'll have to make sure that you have guides that can make sure the blade drops cleanly. If you have access to a good saw, you make a straigh cut in two pieces of wood. Then, you can fit the shuttle into the kerf (the width of the cuts you just made) and it will slide along these guides. As to the shuttle, you need something you can mount a blade in. A razor blade glued to a credit card might work, although this would not be very heavy. Use your imagination.

As to investigations, your questions seem like a good start. Is cut depth proportional to blade height? For constant blade height and weight, how does angle affect cut depth? You might also investigate different material, for example, carrots vs. tiny sandbags. Which are linear (cut depth proportional to blade height) and which are not?

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thank you KDN. this was very helpful. :) –  Jesus-mothic-chick May 27 '12 at 19:22
The angle of the blade doesn't change the pressure - but the angle ensures there is sliding ('cutting') motion of the blade. Micro serrations tear cause local stress concentrations. This is why most cutting is done with a sliding action, not a pushing action. –  Floris Mar 16 at 1:26

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