THAT'S THE WAY THE CHIMNEY CRUMBLES

 

Picture of a Falling Chimney Demonstrating The Break Point. This photo was obtained from the following website: http://aci.mta.ca/TheUmbrella/Physics/P3401/Investigations/ChimneyISM.html



Break-Point Science!

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Introduction

A tall, freestanding, narrow building when ready for demolish can be seen usually as one thing, another building to be removed. Although, if one side is looked closely upon a pattern can be seen. In usual demolition procedure a building would have a section of its base knocked out by a bulldozer or dynamite, giving the building no alternative but to fall to one side. When the building reaches a tilt of 45 degrees, a lateral crack would probably appear near the middle. The lateral crack would force the top part of the building to begin to fall more slowly then the bottom part which would form a V. This occurs because when the building falls the top part has to speed up its movement downwards than the bottom. A crack would appear since the building can’t withstand the bending process and acceleration.

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Purpose

To determine the connection between tall narrow buildings and a breaking pencil point.

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Apparatus

  1. A variety of sharp and "dull" pencils.
  2. Micrometer.
  3. Lego blocks.

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Methods

Step #1

In step one the following pencils were sharpened by twenty turns each of a sharpener; Economiser, Paper Mate, Mirando, Trend, Staedter and Ticonderoga. Each pencil was stood at a writing position at a thirty-five degree angle for “When the pencil snaps #1A”. The pencils were given an amount of force to allow the tips to break. Every type of pencil was given a force of 300,000 Dynes, then the same type of pencils with a sharp tip were given the forces of 500,000 Dynes and then 700,000 Dynes. After every pencil tip was broken they were measured then placed into their own individual little envelope. The pencil tip diameters were measured by measuring the diameter of the broken pencil tip point and the end, then the two diameters were divided and placed in a data table to compare the different types of pencils to the diameter of the tips. The exact same process occurred with “When the pencil snaps #1B” but the angle of the pencil when broken was changed to forty-five degree angle. “When the pencil snaps #1C” went through the same process as #1A but the angle of the pencil was changed to 55 degrees.

Step #2

In step two the same procedure occurred in ‘When the pencil snaps #2 A, B, and C’ as did in step one with its way of doing the angles and forces, except the pencil tips instead of being sharp were dull by doing one hundred back and forth strokes on a piece of loose leaf. The gathering and placing of the data occurred in the same fashion as in step one too.

Step #3

In step three ‘the pencil can break #1A, B and C’ followed the same process as in step one, up until the gathering of the pencil tips. The pencil tips were gathered and measured after every breaking and then put into individual envelops. The pencil tips lengths were measured as well as the diameters. The diameters were calculated by measuring the diameter of the broken pencil tip point and the end, then both numbers were divided to give the diameter and this was done for every broken pencil tip in A, B and C. The length and diameter were put into a data table to be compared.

Step #4

In step four the same process occurred in ‘the pencil can break #2A, B and C’ in the same way as in step two, up until the gathering of the pencil tips. The gathering and measuring occurred in the same way as in step three.

Step #5

In step five Lego was used to build a single free standing structure. Pieces of Lego were placed one on top of the other and a piece of Lego about half the size of the rest was placed and centered on the bottom of the structure of Lego. “They all came tumbling down #1A” was built up to a length when lying down to twenty centimeters then it was stood up on its base. Force was brought upon the top by applying pressure with two fingers on a forty-five degree angle. The angle of force was applied until the structure split in two and before the Lego broke into many sections there could be seen a splitting point where there would be only two sections. The two sections (bottom and top) when placed flat were measured each for their lengths and then the two lengths were put into a data table to be compared against each other. The Lego was placed together again except more was added to make a length of twenty-six centimeters and the same angle of force was used. Thirty-two centimeters was the next length in “they all come tumbling down #1A” with the same angle of force, forty-five degrees.

Step #6

In step six “they all come tumbling down #1B” followed the same process as step five except the angle of force being applied changed to a ninety-degree angle. The gathering of data followed step five too.

Step #7

In step seven “they all came tumbling down #2” followed the same process in step five except the gathering of data was different. When the two sections of Lego occurred, the bottom piece was placed flat and measured for its length. The base piece’s (the half size Lego piece) diameter was determined by measuring the middle of the bottom of the Lego piece. The data taken was placed into a data table to compare the length of the bottom section and the diameter of the base piece.

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Observations







Sharp p. Diameter vs. type


Observation #2


Observation #3


Dull p. Diameter vs. type


Observation #2


Observation #3


Sharp p. Length vs. Diameter


Observation #2


Observation #3


Dull p. Length vs. Diameter


Observation #2


Observation #3


Lego Length vs. Length

45 degrees

90 degrees



Lego Length vs. Diameter (45 degrees)


CLICK HERE FOR PHOTOGRAPHS OF MY PROJECT.

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Analysis and Applications

Demolition of chimney stacks, tall lighthouses, and cylindrical and/or rectangular tall buildings seem to follow a similar "falling" pattern: USually after the dynamite charge or bulldozer or appropriate blows by a crane wrecking ball these begin to fall on one side, rock on an angle of 45 degrees, and start to show a lateral crack in the lower 1/3 of the falling side of the structure. As a result, the top 2/3 portion falls more slowly than the bottom part and the two parts bend forming a "V" shape. These forces on the chimney or other structures have something to do with torque - a sort of twisting force. This torque tends to "cut" the lower section of the structure from the top one. This torque is greatest 1/3 of the way up the chimney. My pencil points and lego blocks also "broke" this way. This indicates that they are a good model. There is also a lateral rupture line going across the diameter of the chimney at this point - this occurred with my pencil points and lego too.

Thus, my pencil points and legos are a good model to help explain the forces and way such real structures or chimneys fall. This could be applied to explain how vertical rock formations on islands and deserts and other areas break and fall.

Pencil points are likely to break as you push down hard when writing. All such breaks are similar to falling chimneys. I noted several points from my experiment:

  1. All broken points were more or less equivalent in length.
  2. Breaking stresses were mostly at the bottom part of the point, with lateral cracks similar to the chimneys.
  3. Bending and breaking forces were greatest at a point where the cross-section diameter of the point is 1.5x the diameter of the writing tip (i.e., a ratio of approximately 3:2) so it showed a rupture at a similar point to a chimney.
  4. Diameter vs. length of broken off points measured a slope of about 2.5, similar to that ratio of falling chimneys. This occurred irrespecived of sharpness of pencil and was best at the angle of 45 degrees...just like falling chimneys.

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Conclusion

My data shows possibly that pencil points and legos are good models for falling structures such as chimney stacks and similar buildings, and may relate to geology (falling rock columns). I wonder if these findings can be applied to long bridges, such as the Confederation Bridge at PEI, aren't these continually falling to the center of the earth?

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Acknowledgements

  • Mr. De La Lis for his continuing encouragement, even during lunch hours!
  • My mom: Thanks for the pencils.

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