Surprising Physics: Falling Flat Boards & Chimneys

[honestrosewater]

Absolutely, and damage would indeed make the chalk break more easily. It needn't even be damage caused by transport or handling, - many manufacturing processes leave imperfections in the product which can cause local weaknesses.

Yeah, but I didn't feel like looking up how chalk is made. Does anyone already know? I'll check later when I have time to kill.

However, since we're observing that the chalk breaks at roughly the same places each time, it's unlikely that this is caused by damage.

Oh, I didn't know they all did break in the same places, but I thought of that too. If you set a box of chalk on a table and gave it a "karate chop"- you know what I mean?- wouldn't that usually cause similar damage to all or many of the pieces? The "karate chop" could be caused by the corner a heavy box falling on it.

 

[brewnog]

Yeah, but I didn't feel like looking up how chalk is made. Does anyone already know? I'll check later when I have time to kill.

I would imagine it's just compressed in a mould. Part of me thinks that it could be extruded, before being chopped up, but at the moment I'm tempted to say that it's just moulded. Either way, there are no inherent flaws as a direct result of manufacturing.

Oh, I didn't know they all did break in the same places, but I thought of that too. If you set a box of chalk on a table and gave it a "karate chop"- you know what I mean?- wouldn't that usually cause similar damage to all or many of the pieces? The "karate chop" could be caused by the corner a heavy box falling on it.

Yeah, but I think that Integral's spent so many hours on the empirical side of his theory that it's probably more general than just one box of chalk. I imagine him to have sourced different brands of chalk from all over the world, under strictly controlled conditions, before testing them all to destruction in his secret underground lair.

 

[honestrosewater]

Yeah, but I think that Integral's spent so many hours on the empirical side of his theory that it's probably more general than just one box of chalk. I imagine him to have sourced different brands of chalk from all over the world, under strictly controlled conditions, before testing them all to destruction in his secret underground lair.

Hm, I guess his secret underground lair isn't so secret anymore.

 

[BobG]

Hm, I guess his secret underground lair isn't so secret anymore.

During dry spells, you can just follow the trail of chalk dust.

Oh, wait. He lives in Oregon.

Integral, dry spells have nothing to do with witches. They're prolonged periods without rain.

 

[honestrosewater]

Integral, dry spells have nothing to do with witches. They're prolonged periods without rain.

I thought witches were women who practiced sorcery and had magical powers.?

 

[BobG]

I thought witches were women who practiced sorcery and had magical powers.?

Which witch? The ones that wear black hats or the sand witches that hang around with dust devils?

 

[Janus]

During dry spells, you can just follow the trail of chalk dust.

Oh, wait. He lives in Oregon.

Integral, dry spells have nothing to do with witches. They're prolonged periods without rain.

Oh we know what those are here in Oregon, sometimes we get them that last as long as a WEEK!

 

[honestrosewater]

Which witch? The ones that wear black hats or the sand witches that hang around with dust devils?

It could be either- I only know they always carry brooms.

 

[honestrosewater]

Oh we know what those are here in Oregon, sometimes we get them that last as long as a WEEK!

Do yours carry brooms?

 

[Integral]

I would imagine it's just compressed in a mould. Part of me thinks that it could be extruded, before being chopped up, but at the moment I'm tempted to say that it's just moulded. Either way, there are no inherent flaws as a direct result of manufacturing.



Yeah, but I think that Integral's spent so many hours on the empirical side of his theory that it's probably more general than just one box of chalk. I imagine him to have sourced different brands of chalk from all over the world, under strictly controlled conditions, before testing them all to destruction in his secret underground lair.

My testing was done sporadicly over my 15 years in academia, if front of many different black boards in many different class rooms. Most of the chalk I have dealt with has been of very similar dimensions, but I have allowed dimension as a critical parameter.

Now as for tracks into the secret lair, it is not clear? Are those \pi tracks from Bobs \pi feet or dusty chalk track?

I am sure that broom carrying lady was just the janitor sweeping up the chalk tracks (which are much easier to clean up then \pi tracks) and not a witch!

As I write, I notice that something strange is happening outside, there is some unusual form of energy pouring through my windows, and the clouds all seem to be blue?
Janus, what is that big yellow thing in the sky?

 

[Janus]

Do yours carry brooms?

Sure. They use them to keep the storm drains clear.

 

[Janus]

As I write, I notice that something strange is happening outside, there is some unusual form of energy pouring through my windows, and the clouds all seem to be blue?
Janus, what is that big yellow thing in the sky?

I don't know, But I bet you is has sumptin' to do with one of dem der' "dry spells" cast by a "sand witch".

 

[Integral]

I don't know, But I bet you is has sumptin' to do with one of dem der' "dry spells" cast by a "sand witch".

That sounds reasonable... Now I am hungry! A sandwitch and some round \pi sounds real good.

 

[Janus]

That sounds reasonable... Now I am hungry! A sandwitch and some round \pi sounds real good.

Round \pi? I thought \pi r^2?

 

[Integral]

Round \pi? I thought \pi r^2?

That is a common myth. When was the last time you ate a square \pi?

 

[Janus]

That is a common myth. When was the last time you ate a square \pi?

It was a Shepherd's \pi.

 

[honestrosewater]

I like to fit square \pi into a square meal; It's more efficient that way.

 

[Crosson]

This chalk business is reminiscient of Feynman's conjecture: If you grasp the two ends of a dry spaghetti noodle and break the noodle by bending, it is almost impossible to break it into any less then 3 pieces.

 

[Mk]

That is a common myth. When was the last time you ate a square \pi?

I usually encounter it in a triangular prism form.

http://www.rockfield.co.uk/images/chimney_collapsing_real.gif
This chimney broke into \pi pieces.

So tomorrow I'll settle this - if I remember to buy chalk. I'll try and get the sidewalk form as well. I don't have a highspeed camera.

 

[Mk]

I bought the chalk today, but I'm going to do it tomorrow. I'm confident it will break into pi pieces. Happy trails!

-Mr. Smith

 

[honestrosewater]

I bought the chalk today, but I'm going to do it tomorrow. I'm confident it will break into pi pieces. Happy trails!

-Mr. Smith

Watch out for the witches and shepherds.

 

[hypatia]

Now he even has me waiting for his results

 

[PerennialII]

... he better come up with a detailed report ... gotten to the point that have to make someone do a lab assignment (for real) about this topic .

 

[Mk]

I forgot to do it! Oh no, its 11 o'clock, I will do it tomorrow.

 

[Mk]

So with my box of 16 3 and 1/4 inch, long-lasting non-toxic plain RoseArt white chalk, I would have to conclude: Myth busted.

Four trials, at 3 heights: 36", 42", and 48" inches.

At 36 inches:
Trial 1: 2 pieces (1:1)
Trial 2: 2 pieces (2:1)
Trial 3: 4 pieces (1:1:1:1)
Trial 4: 1 pieces

At 42 inches:
Trial 1: 2 pieces (1.5:1)
Trial 2: 1 pieces
Trial 3: 1 pieces
Trial 4: 3 pieces (1:4:1)

At 42 inches:
Trial 1: 2 pieces (2:1)
Trial 2: 2 pieces (1:1)
Trial 3: 1 pieces
Trial 4: 3 pieces (4:1:4)

Not one time did the chalk break into pi pieces.

Sorry kids.

 

[honestrosewater]

No wonder - you got long-lasting chalk!

 

[PerennialII]

... now for starters someone fit a Weibull distribution to the results please ... we'll see what kind of brittle material we're talking about.