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PHYS 438 / BIOL 438: ProjectsIt is not too early to think about what you're going to do! If previous years have been any indication, students have been loathe (of course) to get started on their projects. However, once they actually got started, they discovered that i) They really enjoyed it! and ii) There isn't enough time. Here is a list of the projects from 2004 (vague titles only). The project abstracts and some of the full reports remain from 2003 as an example of what might be expected this year. Project AbstractsLighter weight or Heavier weight: What is better for the sport of ski jumpingAuthor: Nils Antons Abstract: Ski jumping, like many other sports, is a sport in which the body weight of an athlete plays a large role. The results of this project indicate that lighter skiers can jump further based solely on their weight. The knowledge that being light is advantageous enables ski jumpers to adjust their training and eating plans accordingly to gain a competitive advantage. Lighter skiers can compensate for slower inrun velocities by having favorable flight phase lift and drag forces. In this project two ski jumpers of different weights, a 60 kg and an 80 kg one, with the same body composition where used. Their inrun and flight phase velocities, drag forces, and lift forces were analyzed in one-second intervals. The major forces considered to be acting on the skiers in this project where the force of Gravity, the Force of Lift, and the Force of Drag. The force of friction exerted by the skies onto the snow during the inrun was considered to be minimal and was neglected. The newly constructed Ski Jump in Innsbruck was used as a reference for the jump site parameters. The ski jump is comprised of four phases; the inrun, the jump off, the flight, and the landing phase. They were analyzed separately in this project Key words: Ski Jumping, Lighter, Gravity, Force of Lift, Force of Drag. Hardcopy only so far Walk or Waddle?Authors: Caroline Jiang & Hayley Shen Abstract: Griffin and Kram (2000) found that penguins waddle because it is more energetically efficient than walking. Although humans are obviously different from penguins both anatomically and physiologically, a waddling gait can also be observed in certain types of humans. Instead of walking, as most people do, pregnant women, and excessively overweight individuals tend to waddle. This study investigates the energetic requirements of waddling as compared to walking under two different conditions: overweight, and normal weight. We hypothesize that the total energy cost (work) of waddling is less than the total energy cost of walking for "obese" or pregnant people. The opposite is true for those who are within the "normal" weight range. How Fast a Muscle can Contract?Author: (Arash Takshi) Abstract: How fast a muscle can contract? How fast a runner can run? How fast human body can react against a phenomenon? How fast a bird can flap? There are a lot of questions like these that is important for human to know. Although each question should be investigated individually and for each case all related parameter should be considered, the common question among all of them is "How fast a muscle can contract as an actuator?" To finding out the answer of this question first of all the structure of muscle should be investigated from different views. Physiological views, chemical reactions, mechanical behaviors will be discussed in the first chapter. Different type of muscle fibers and the architecture of muscle will be explained in the second chapter. In the chapter three modeling and experiments results will be elucidated. Finally in the last chapter by the use of the model and information some calculation will be run to give a sense about the speed of muscle. It is raining catsAuthor: Margaret Kwok Abstract: Cats are known to right themselves by rotating their bodies while falling through the air and despite being released from almost any position, they are known to have the ability to land on their feet. Several mechanisms have been proposed to explain how cats are able to reorient themselves in the air. All observations and measurements were made on my averaged sized house cat, Wong Wong. A cat was simplified into three two part models and the models were used to test whether or not a one joint, two segment model would be sufficient in explaining how a cat is able to rotate in the air to land feet first when dropped from an upside down position in 0.3 s. The first model consists of one segment forming the tail and another forming the body and the head and the results show that the cat would have to have an angular velocity of 331 rad/s and rotate 15 times. The second model has the cat divided into a head and body and the results show that the head would have to rotate at 1141 rad/s about 54.5 times. The third model divides the cat in half with the first half consisting of head and upper body and the second half consisting of the tail and the lower body and results show that the cat would have to rotate at 15 rad/s and it would have to rotate 257 degrees. The models were restricted to rigid two cylinder, coupled systems that revolved around one axis to allow the application of simple physics equations. The calculations suggest that the cat can rely solely on a two segment one joint system to rotate itself in the air using the third model but not the first two. How a Gecko sticks to a wallAuthors: Sophia Lee & Colin Ng Abstract: Aristotle observed that geckoes not only climbs trees, they can run in downward direction, or even horizontally across. The source behind the gecko's amazing ability to climb has been found to be London dispersion forces generated by extremely close contact to a the wall from micro-fine hairs (setae) ending in keratinous tips (spatulae). Literature values indicate that a gecko with a total footpad area of 4 cm² can produce 88N of adhesive force, enough to support many times its body weight. We examine several reasons for this seemingly generous endowment from nature. The physical details of the gecko's adhesive ability are analyzed: the contact area of individual spatulae is deduced from electron micrographs, the theoretical packing arrangement is deduced statistically. Using a Hamaker constant of 10-19 J for keratin, we determine the nominal and maximal adhesive force generated. Finally, we examine the feasibility of learning from this marvel of evolution to create a device that will allow us to have superhero powers and climb walls like Spiderman.
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Killer Whales with Killer TailsAuthor: Jeanette Lim Abstract: Killer whale pods sometimes hunt herring by corralling the fish into a tight ball near the ocean surface and stunning them with underwater tail slaps before eating them. I asked if this was possible with an above-water tail slap at the ocean surface, without any physical contact between fluke and fish. Basic physics concepts used were conservation of momentum (m[Fluke]u[Fluke,i] = m[Water]u[Water,f]) and pressure waves (I= 1/2 pvu[o]²= dp²/2pv). When a whale's fluke collides with the ocean surface, the fluke's momentum is transferred to the water directly underneath. A pressure wave with intensity, I, is created that exerts a pressure on anything in its path, including fish. The sound pressure level fatal to fishes (using guppies as a representative species) is 230dB//1uPa, corresponding to an intensity of 3.252 x104 Watt/m². Major assumptions were that all of the fluke's momentum is transferred to the water through a collision without any losses, and that decreases in pressure wave intensity are negligible because the ball of fish is near the water surface, close to the collision. Results for a 7m long (average length) whale were that with a collision time of 0.00455 seconds or less, which corresponds to the fluke going into the water a maximum depth of 3.28 cm, a pressure wave with an intensity of 3.252 x104 Watt/m² or higher could be generated. It was concluded that given the assumptions, it is possible for killer whales to use above-water tail slaps to stun or kill fish in the water below, if the collision time between fluke and water is sufficiently short. The Ideal CyclistAuthor: Russel Muthanna Abstract: This paper attempts to answer the question of what is better for the cyclist - to be heavy or light. In this analysis, it is assumed that a larger rider is more powerful. As well, the effects of the larger cyclist's bigger bike are ignored, as they are negligible. A theoretical study will be done on three separate cases: cycling uphill, cycling downhill and cycling on flat land. As well, data from powerlifters will be analysed to establish the validity of the findings. The results show that lighter cyclists have an advantage riding uphill as lighter individuals have a greater power to weight ratio. In addition this result is supported by an analysis of the powerlifter data. In contrast, heavier riders have a distinct advantage when going downhill, due to a greater increase in mass when compared to increase in drag force (due to increased surface area). Finally, heavy riders also have an advantage on flat land due to the greater increase of their strength (according to equal bending scaling) when compared to the increase in drag force they experience. Can you run on water? (He can)Author: Andrew Yadegari Abstract: The Basilisk lizard is among the small number of animals that can run on water. It stays afloat a mechanism involving surface tension. When running, they slap their long feet on the surface of the water, creating an air bubble that lasts only a fraction of a second. The buoyancy of the air bubble helps push the lizard's foot out of the water; providing most of the force necessary to lift the lizard. However each step must be taken very quickly, meaning that the lizard needs to run at speeds of 10 km/h. A crucial feature of the lizard's morphology is the flaps of skin on the sides of each toe. The flaps open when the foot hits the water, increasing the area of the bottom of the foot, and close when the foot is lifted out of the water, decreasing the friction drag. The lizard reaches an upper limit in size around 200 g, at which point it can barely support 110 % of its own weight. Hardcopy only so far How do Insects Wing It?Author: Jacqueline Yap Abstract: Intrigued by the delicate structure of the iridescent insect wings, I wanted to find out how much an insect's membranous wing weigh. Investigating the wing is important as the success of insects as terrestrial animals is due to their ability to fly. I approached the problem by reading studies done on insect flight, and came across a link between asynchronous muscle contractions and the wingbeat oscillations. Asynchronous muscles are unique, as each contraction is not dependent on a neural impulse; instead, they are controlled by the muscle itself which has the intrinsic ability to oscillate, the elasticity of the thorax, and wing oscillations. I calculated the wing mass of the bumblebee Bombus terrestris by modeling the asynchronous muscle and wing into a mass spring oscillator. The bumblebee wing mass was found to be 170 mg. This was not what I expected as wings are very light (<1mg), perhaps there was an error in approximation and calculation of the spring constant, k or the additional mass is due to the air mass the wing pushes around during flight. Key words: asynchronous muscle, wing, spring, insect flight, Bombus terrestris. Birds on Mars. Is it possible?Author: Vincent Yu Abstract: The planet Mars has been terriformed and scientists have managed to make living conditions on the planet every bit as identical as that of the Earth. With exception to the gravitational force of the planet and the atmospheric density, factors such as atmospheric composition, temperature, and vegetation on the planet accurately mimic our planet. Can birds now be introduced on the ``new'' Mars and proliferate successfully? Since gravity is weaker on the surface of Mars than it is on Earth, flight should be easier on the planet as the force of gravity pulling the bird down towards the planet is much less. However, the density of the planet's atmosphere is only 1/100 th the density of that of Earth. Is this density adequate to provide enough lift force in the bird's wings for it to fly properly? It was found that a Canadian goose (out representative bird) would have to fly at a speed of 730.8 km/hr in order to have its wings generate adequate lift to glide over the Martian surface. This is not physiologically possible simply because birds aren't capable of generating enough power for the thrust required to reach such a speed. It was also found that even if the goose flew at an altitude of 0 metres (as compared to 1000m) where the air density was at its greatest, only about 3% of the required lift could be generated. |
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