A Date With Physics


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A Date With Physics

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  2. 2. “A date with physiKs”<br />Dr. Ralf Widenhorn<br />Portland State University<br />Department of Physics<br />ralfw@pdx.edu<br />Illustrations by Alan Courtay<br />alancourtay@yahoo.com<br />
  3. 3. So now can someone give me the energy of a vacuum?<br />
  4. 4. “A date with physiKs”<br />date<br />What is it?<br />An appointment to meet at a specified time; especially: a social engagement between two persons that often has a romantic character<br />PhysiKs<br />What is it?<br />A science that deals with matter and energy and their interactions. From ancient Greek: physics, "nature“.<br />
  5. 5. In 2004, Ralf successfully decomposes the forces on his bicycle and earns a PhD...<br />
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  7. 7. Cell phone inside<br />
  8. 8. Faraday cage<br />What is it?<br />An enclosure formed by conducting material or by a mesh of such material. Such an enclosure blocks out external static electric fields. <br />What is going on?<br />Radio waves used for telecommunication are electromagnetic waves. The metal enclosure prevents some of the electromagnetic radiation from reaching the phone. <br /><ul><li>Metal used in buildings is a main reason why you may not have cell phone reception indoors.</li></ul>Please silence your cell phone! <br />
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  13. 13. Bernoulli Principle<br />What is it?<br />A principle in hydrodynamics: the pressure in a stream of fluid is reduced as the speed of the flow is increased.<br />What is going on?<br />The airflow is larger under the sphere than above, causing a net upward force. When the sphere moves to the right the airflow increases on the left and decreases on the right causing a restoring force that pushes the sphere back into the center. <br /> Lift of Airplanes<br />
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  18. 18. Question 1 <br />Which soup can will go down the incline the fastest?<br />a.) Chicken broth<br />b.) Cheddar Cheese<br />c.) Vegetable Beef<br />d.) New England Clam Chowder<br />e.) All cans will go at the same speed<br />
  19. 19. Question 1<br />Which soup can will go down the incline the fastest?<br />a.) Chicken broth<br />
  20. 20. Moment of inertia<br />What is it?<br />A measure of the resistance of a body to angular acceleration about a given axis that is equal to the sum of the products of each element of mass in the body and the square of the element's distance from the axis.<br />What is going on?<br />As the cans roll down the incline, potential energy is converted into kinetic energy of translation and rotation. The more of the can’s content rotates, the more energy is in the rotational motion. This decreases the energy available for the translational motion and decreases the translational speed. <br /> Try with a container of frozen and liquid lemonade<br />
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  23. 23. Conservation of momentum<br />What is it?<br />the principle that the total linear momentum in any isolated system is constant, provided that no external force is applied.<br />What is going on?<br />The initial momentum of the system is zero. Hence, the final momentum must be zero. The tennis ball is ejected at a very large speed which causes the heavier cannon to recoil with a smaller speed backwards. <br />Mcannon*vcannon = mTBall*vTBall<br />
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  25. 25. A lesson about things...<br />
  26. 26. The heat of the<br />sun and the blue of the sky are both electromagnetic waves!<br />
  27. 27. Twee twee!<br />The singing of<br />the bird reaches<br />our eardrums as mechanical waves!<br />
  28. 28. The wavelets that<br />propagate at the surface of water, again these are waves!<br />
  29. 29. All of this is ruled by <br />the same beautiful law:<br />
  30. 30. What a shockwave!!!<br />
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  32. 32. center of mass<br />What is it?<br />The point in a body or system of bodies at which the whole mass may be considered as concentrated.<br />What is going on?<br />If the "plumb line" dropped from the center of mass falls outside the area of an object's (you) base of support (in this case your toes), an object will topple (no matter how flexible you are). <br />As of now, the Leaning <br />Tower of Pisa is standing…..<br />
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  34. 34. Non-Newtonian fluid<br />What is it?<br />A non-Newtonian fluid is a fluid for which viscosity is variable, based on applied stress.<br />What is going on?<br />Cornstarch mixed with water " (2 parts corn starch to 1 part water) is a shear thickening non-Newtonian fluid sometimes called "ooze”. <br />If you punch a bucket full of ooze, the stress introduced by the incoming force causes the atoms in the ooze to rearrange such that it behaves like a solid. If you shove your hand into the ooze slowly, however, it will penetrate successfully. <br /> Quicksand is a non-Newtonian fluid that is shear thinning.<br />
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  36. 36. Question 2 <br />Which can will float?<br />a.) Coke<br />b.) Diet Coke<br />c.) Diet coke and coke<br />d.) neither<br />
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  38. 38. Question 2 <br />Which can will float?<br />b.) Diet Coke<br />
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  40. 40. Archimedes principle <br />What is it?<br />Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.<br />What is going on?<br />The density of water is 100g/100ml . <br />Any object with a smaller density will float , any with a larger density will sink. <br />The density of regular pop is 374g/355ml whereas the density of diet pop is 354g/355mL.<br />Regular pop has about 35 g of sugar; diet pop has about 2 g of aspartame. <br />
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  43. 43. I was living there until my parents converted my room into a bed & breakfast!<br />
  44. 44. Index of Refraction<br />What is it?<br />The ratio of the speed of light in a vacuum to the speed of light in a medium under consideration.<br />What is going on?<br />When light travels from a medium with one index of refraction to another, some of light gets reflected and some light is refracted.<br />The jelly marbles have almost the same index of refraction as water. The absence of reflection and refraction makes them almost invisible in water. <br />The jelly marbles start out as hard crystals, but they are actually made from a superabsorbent polymer (Polyacrylamide ) that absorbs 300 times its weight in water. <br />
  45. 45. Diffraction grating<br />What is it?<br />A system of close equidistant and parallel lines or bars ruled on a polished surface to produce spectra by diffraction.<br />What is going on?<br />The CD and DVD serve as a <br />grating that splits light into <br />several beams travelling in<br />different directions. <br />The directions of these beams depend on the: <br /><ul><li> Separation of the tracks (1.6 mm for the CD and 0.74 mm for the DVD)
  46. 46. Wavelength of the light. </li></ul>The larger the wavelength and the tighter spaced the grating, the more the beams diverge.<br />
  47. 47. Sorry but we don’t have chemistry!<br />How about physics?<br />
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  52. 52. Standing waves<br />What is it?<br />A single-frequency mode of vibration of a body or physical system in which the amplitude varies from place to place, is constantly zero at fixed points, and has maxima at other points.<br />What is going on?<br />When stimulated, an object likes to vibrate at particular frequencies so-called resonance frequencies. The stick-slip of the fingers stimulates an oscillation and a standing wave is formed oscillating at the resonance frequency. <br /><ul><li>Squeaking chalk on a blackboard
  53. 53. Frets and guitar</li></li></ul><li>
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  55. 55. Question 3 <br />The shorter rod will<br />a.) have a higher pitch.<br />b.) have a lower pitch.<br />c.) won’t vibrate at all.<br />
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  57. 57. Question 3<br />The shorter rod will<br />a.) have a higher pitch.<br />
  58. 58. Can I see you again?<br />Sure! Call me...<br />How did he build that cage again?!?<br />
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  61. 61. Atmospheric pressure<br />What is it?<br />The force per unit area exerted against a surface by the weight of air above that surface in the Earth's atmosphere.<br />What is going on?<br />The standard atmospheric is equal to 101,325 Pascal (N/m2) or 14.696 psi (pounds/square inch). If a partial vacuum is formed in a container, the atmospheric pressure has no counter acting force and can collapse even a sturdy barrel. <br />
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  63. 63. Inertia<br />What is it?<br />The property of matter by which it retains its state of rest or its velocity along a straight line so long as it is not acted upon by an external force. <br />What is going on?<br />The force acting on the dishes is friction. The maximum frictional force depends on the surfaces of the table cloth and the object on it. Pulling the table cloth quickly allows this force to act only over a very short period of time. This may not result in any significant movement of objects. <br />
  64. 64. Albert Einstein, 1905<br />Sir Isaac Newton, 1687<br />Erwin Schrődinger, 1926<br />Thank you guys!<br />Daniel Bernoulli, 1738<br />Michael Faraday, 1839<br />Dr Ralf Widenhorn, tonight<br />