The Worley Expo Brings Insights on Tornados
The extreme conditions of a tornado can force a straw into a telephone pole. This is a common phenomenon associated with the destructive force of this type of windstorm. The feat itself is based on much conjecture, however the folks over at the National Oceanic and Atmospheric Administration say that tornadoes are “certainly strong enough to turn otherwise harmless items into deadly missiles” (http://www.ncdc.noaa.gov/oa/climate/severeweather/tornadosafety.html). This is demonstrated by the images below:
A harmless record album became a disc of terror through the awe-inspiring forces contained within a tornado.
A slat of wood was driven through a fairly thick palm tree during a storm with gale-force winds.
The dynamic forces within a tornado are complicated, but not entirely incapable of being re-produced in a lab, as the masterminds behind Discovery Channel’s MythBusters demonstrated when they attempted to put the “straw through a telephone pole” theory to the test. The results were semi-fantastic and resulted in the straw pushing one-fourth of the way into a palm tree, at 320mph.
At Pie, we tried something a little lower-key, and had two of our forensic investigators – Brad Stolz, P.E. and Tyler Schwein, E.I.T. – estimate the velocity needed for a Spyderco knife to pierce through a 2×4. These calculations evolved and turned into a popular contest that was featured at the 2012 Worley Expo in Houston, Texas.
Although our investigation involved less panache than the MythBusters experiment, we created a unique display for the Spyderco knife that illustrated this phenomenon, and asked two very concise questions:
- What velocity (MPH) is required for the knife blade only to pass through this 2×4? (as you see in the picture below)
- Assuming the knife will completely penetrate (pass all the way through) the 2×4 at 122mph –yes or no – does the orientation of the knife matter? (Blade first or handle first?)
A local Texan guessed the speed, 77/mph, spot on (without doing any calculations), and was also correct regarding the orientation of the knife. And the reward for the correct answer? The Spyderco knife of course. We received a lot of great comments about the contest and many shared their own stories regarding the amazing forces of tornadoes. All was well with the world once again.
But…wait; is there a viable explanation for how an object of small mass can penetrate another object of greater mass? There certainly is!
Vince Calder on the “Ask a Scientist” portion of the NETWON website simplifies, saying, “if I jump into a lake from a height of 1 meter, I just sink and make a splash — no harm. But if I jump into the same lake from an airplane at 1000 meters above the surface, I’m a pancake. I might just as well hit solid ground. The reason is: at the speed with which I hit the water is so fast, the water does not have time to “get out of the way” so it becomes essentially a solid. This is what happens to straws etc. driven by tornadic winds.” (http://www.newton.dep.anl.gov/askasci/phy00/phy00325.htm).
Another interesting fact about these objects becoming lodged in things is that the object lodged is usually intact, showing very little damage.
This question and numerous others are constantly being considered in the research for finding out how tornadoes work and how to better predict them. If this can be accomplished in the near future, it is hopeful that loss of life and property damage may be reduced.
In the meantime, you can rest assured Pie will keep providing forensic engineering expertise in catastrophic situations, helping you solve complex challenges as you deal with insurance claims.