Breaking a drinking straw with karate chop

guy3288

try do a karate chop on a drinking plastic straw with its 2 ends held tight by a friend.
You just can't break it no matter how hard you hit it with your bare hand.
it's just too resilient, or it will just slip off your friend's grips.



However if you just thread the straw through a piece of ice (ring shaped ) and you do a karate chop on that piece of ice, the straw suddenly become so "brittle" and it will break easily.

Can anybody explain why this is so??

First i thought the straw was cut by the ice, but then on closer look i found that was not the case.

So i am looking for experts in physics to help. Anybody please?

FlexGunship

Firstly, allow me the luxury of welcoming you to these forums! Welcome.

Secondly, I think you'll find that most folks here have not tried what you are talking about, nor are most of us adequately equipped to reproduce the test (I have neither a ring of ice, nor a friend).

Could you possibly provide some evidence that what you're claiming is true? A video would be very helpful. Otherwise, maybe you could give us a couple of diagrams or a more detailed description of the setup.

Although this might belong in a different forum here, I'll treat it as though it is a claim requiring debunking (since I'm not sure I believe the claim; its very interesting).

guy3288

hi there, thanks for your response.

What i wrote up there is definitely true. I saw it with my own eyes, and it is easily reproduceable. What i am looking for is the explaination behind that 'feat'. How that piece of ice could help in breaking the straw.

I saw my kids doing it and apparently they have learned it from their friends in school.


The straw that we use over here is not that thick huge straw that you see used in fast food restaurants like Mc Donald Or KFC.s but the ordinary straw used by roadside food hawker and also coffee shops.

And the edible ice mentioned here is the commercially available type which looks like a cylindrical ring.

I am sure some of you in here would have seen the type of drinking straw and the edible ice i mentioned.

I will try to take some pictures and upload it here if that is allowed.

Ivan Seeking

Welcome to PF.

You don't need to provide any evidence for this one, but pictures would help to clarify the situation.

Do you chop the straw at the point of contact for ice ring?

guy3288

I dont hvae the commercial ice with me, but here is how it's done.

http://yfrog.com/nbimg2354kj
http://yfrog.com/0simg23550j
http://yfrog.com/2gimg2356ij

dav2008

Polymers tend to become brittle at lower temperatures. It's very possible that the ice cools the straw to the point that the middle section becomes brittle and easy to break.

Hepth

Can you try it with something else cylindrical yet rigid?
-Perhaps the edges give a point for which your hand to apply the force, thus greatest pressure on a single line instead of the width of your soft hand.

Does it shatter the ice? I'd assume not as the ice should be pretty thick.

Can you do it with a few seconds of putting the ice on the straw? If not this would suggest the above(day2008) comment.

Go freeze a pen in an icecube and try this :)

yaang

This. İn fact most materials become more brittle in lower temperatures. I'm sure everyone has seen rubber bands or leaves shattering like glass after being dipped into liquid nitrogen. If not do a quick youtube search it's pretty interesting to watch if you've never seen it before.

guy3288

thanx for the comments.

so it's possibly the cooling effect and may be also the edges of the ice that allow more concentrated force to be applied.

it would be nice to do an experiment as you suggested, use ice and another similarly rigid ring to compare. How about marking the straw at the points that correspond to the edges of the ring and see if the breakage occur at those points?

Interesting.....