A New Perspective on Why It Is Important that We Teach Chemistry and Physics
Two years ago, on a Friday in April, I watched a s my nine-year-old son won a foot race by a good 20 or 30 feet and thought nothing of it. Aiter all h e always wins races, he's very fast. l h e n t y nights later, I watched my son walk across my bedroom, hesitantly and wobbly, but I had never been prouder of him. The intervening 20 days gave me a new uersoective of the imoortance of chemistnr and uhvs. . ics in our lives and why w e must communicatithat in our students. I would like to share this pcrspective with you. Less than 30 minutes after wiming the rare my son told me that he could not move his lcfl hand. For the next two days he continued to losc more and more olhis left side body function and finally on Saturday night, he could no longer urinate. At that point we wok him to the hospital where the doctor immediately ordered a set of rerehral spine X-rays and a CT scan of the head and spine. These scans showed
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Journal of Chemical Education
no abnormality so an MRI scan was ordered for the next morning. The MRI scan showed that there was a sign& cant amount of blood accumulated amund the front of the spinal cord and a n early diagnosis of an arterial venous malformation in the spinal cord was made. Intravenous steroids were administered to reduce the swelling amund the cord. Later on Sunday the local nenmsurgeon told us that there was nothing that could be done for him locally and suggested that we move him to a large research hospital. Monday morning found us in Gainesville, FL a t Shands Teaching Hospital where the pediatric neurosurgery group began studying the MRI scans. Monday afternoon the neurosurgeons performed a n angiogram in which a plastic catheter was inserted into one of my son's veins near the groin and snaked up to the neck area. The progress of the catheter was followed using a series of X-ray scans that essentially gave a TV picture of the catheter moving
through the veins and arteries. Once the neck region was entered, an iodine containing dye was inserted into the catheter and the flow of blood in the neck area could be monitored on the TV screens. This revealed a hole in one of the arteries or veins in front of the spinal cord. (This particular problem is called a fistula and was probably a congenital problem that fmally surfaced.) Next came the discussions of what to do and how to do it. On Wednesdav the decision was made to perform another angiogram but this time its purpose was to shut off the flow of blood to this artem. The angioeram was scheduled for Thursday morning. A; 9 0 0 AMh'was whisked off to start the procedure. For the next two hours a slow blockage of the artery was performed in the following manner. First the catheter was inserted from the groin to the neck area and positioned just in front of the fistula. Then roughly one inch longsilk threads, that had been soaked in a oolvvinvl alcohol solution. were inserted into the cathete; and lodged in the a r t e i just in front of the fistula. As these threads formed a blockage in the artery, the polyvinyl alcohol caused the blood to clot and seal off the artery past the point of the blockage. As the artery was sealed off and blood clotting continued, the artery that had caused the paralysis was effectively rendered useless. This decreased the pressure on the spinal cord so that osmotic forces could begin removing the blood from the spinal cord area. Friday morning the physical therapist arrived and for the first time in a week my son walked a little on his own. On Mondav a third aneioeram showed that the blockage was compl& and discharge from the hospital followed i n Tuesdav. Further ~hvsicaltheraov took up the remainder of this week and b n Sunday, two weeks after the initial event, my son returned home. By Tuesday he was hack in school full time. He walked slowly and hesitantly to class, but he walked on his own. Every time that I have told this story, the response has been that it is a miracle of modem medicine, which it certainly is. But there is another miracle here that we teachers need to inform our students of and that is the miracle of some old, middle-aged, and modern chemistry and physics. Not that many sears ago . my . son would have been written-offas unsalr&able because we could not see what his problem was nor get to the arca to fix it. Now with X-rays. b~ scans, MRI sc&~ and angiograms seeing the is a much simpler . process. When I hear CT scan. MRI and angiogram the names Roentgen, discoverer of X-rays in 1895, Bloch and Purcell, discoverers of NMR in 1946, and Shockley, Brattain and Bardeen, discoverers of the transistor in 1948, rush to my thoughts. The steroids that were administered to relieve the oressure in mv son's spinal cord were probably made from a process that was initiated bv Woodward as he determined how to svnthes~zesteroids i i 1951. The catheter and the polyvinyl hcohol, that were so instrumental in blockina . the arterv... are the direct descendants of the pioneering work on polymers done by I3aekrland in 1907 and Carothers in 1928. All of these discoverers were "doctors" of the Ph.D. variety not the M.D. type. What this experience has brought to my attentionis that neurosurgeons are the hands of modern medicine and the miracles that it can make. The spinal cord of modem medicine is chemistry and physics. If the blood supply to the spinal cord is choked off, as we fear will happen in this era of lack of interest in the phvsical sciences. then the ultiof modem medicine. That is mate result will he whv i t is imwrtant that we teach chemistrv and ohvsics and do a gobd job a t it. Our students must real&e-that chemists and physicists are every bit as important to the &
recovery of my son's health as the neurosurgeons that applied the fruits of the labor of chemists and physicists. Who knows what the miracles of modern chemistry and physics will give us tomorrow. Charles H. Atwood Mercer University Macon, GA 31207 Rolling Happy and Unhappy Balls and Their Coefficients of Friction
To the Editor: The article "Happy and Unhappy Balls: Neoprene and Polynorbornene" [J. Chem. Educ. 1990,67,198-1991 contains misconceptions about friction and rolling motion. A ball made from neoprene rubber (a Yla~ov"ball) rebounds elastically when bounced, while' a baii k a d e from polynorbornene (or Norsorex. a n "unhao~v"ball) does not bounce. When the two t&es of balls'&e allowed to roll down a n inclined plane, the "happy" ball always beats the "unhappy" ball to the bottom. The authors claim that The "unhappy" (polynorbornene) ball rolls more slowly because of its higher coefficient of friction, which makes this type of rubber ideal for racine car tires. for which meat road adhesion is needed at high speed. The coefficient of friction involves surface friction, which opposes the sliding motion of two surfaces in contact. While the coefficient of friction of polynorbornene may be meater than that of neoprene. an exoeriment involvina Foiling (without slipping) Lotion will not give any inform: tion about coefficients of surface friction. The experiment required to compare coefficients of surface friction would have to involve sliding, not rolling, of the balls. Surface friction does not dissipate kinetic energy in the process of rolling as long as no slippage occurs. Ideally, all rigid homogeneous solid spheres should roll down an inclined plane with the same acceleration and have the same velocity at the bottom of the plane, independent of the mass, radius, or density of the sphere. (The acceleration of a rolling solid sphere is 517 that of a n object sliding down the same plane with no friction, and the translational velocity of t&e rolling sphere by the time it reaches the bottom of the incline is only (5/7)'n as great as if i t had been sliding.) A larger coefficient of friction does not slow down the rolling motion-it only assuresthat the sphere will roll, rather than slide, down the incline. How, then, can one explain the observation that the unhappy hall always loses the race down the plane? A possible explanation may be that there is greater adhesion (different from surface friction) between the Norsorex ball and the plane resulting in a larger trailing edge force which slows down that ball. Another more likely explanation is that in the unhappy ball, internal irreversible deformation (perhaps on the microsco~iclevel) occurs durina rollina. -, absorbing some of the energy and leaving less energy available as translational kinetic enerm. This internal irreversible deformation is sometimes referred to as rolling friction (perhaps a misnomer), but it is hard to see how this property could be beneficial in racing tires. This explanation also correlates with the bouncing behavior and the behavior of the two balls when compressed in a vise. The happy . . . ball is deformed under stress but is capable of quickly returning to its originul shape oncr the stress is removed, thus recovering the enerby of deformation. However, when the unhappy ball is deformed, u,hether in a vise or during a bounce, it does nor quickly return to ~tsori'lnal shaoe once the stress is rcmoved Thus. when the unhaoov baliis bounced, kinetic energy is transformed irreversIb'6 into internal energy of the ball as deformation and heat. A
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Volume 70 Number 10 October 1993
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