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# lecture17 - Physics 231 Lecture 17 Main points of todays...

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ain points of today’s lecture: Physics 231 Lecture 17 Main points of today s lecture: Viscous flow Poisseuille’s law d Av F •T e m perature   L P P R t V 8 2 1 4 Thermal expansion T A A TL L 0 ; ; Ideal gas properties: T V V 0 k RT V KE V N v m V N P T Nk nRT PV B 3 2 2 1 3 2 2 T k E K KE B 2 3

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Conceptual question Blood flows through a coronary artery that is partially blocked by deposits along the artery wall.Through which part of the artery is the flux (volume of blood per unit time) largest? – a) The narrow part. – b) The wide part. – c) The flux is the same in both parts. If it increases, where does the blood come from. If it decreases where does the blood go?
Conceptual quiz A blood platelet drifts along with the flow of blood through an artery that is partially blocked by deposits. Assume that viscosity can be neglected. As the platelet moves from the narrow region the wider region it ould experience to the wider region, it should experience – a) an increase in pressure. ) no change in pressure – b) no change in pressure. – c) a decrease in pressure.

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Viscous flow iscosity limits the relative velocity between a Viscosity limits the relative velocity between a fluid, the walls of its container and between two nearby points in the fluid. Assume a viscous fluid between two solid surfaces. Because the fluid “sticks” to the surfaces a force is required to move the upper surface relative to the lower surface. d Av F Material at T=20 o C η is the viscosity coefficient SI units are Ns/m 2 cgs units are Poise air 1.9x10 -5 N s/m 2 water 1.0x10 -3 N s/m 2 1 Poise = 0.1 Ns/m 2 glycerin 1.5 N s/m 2
Poisseuilles’s Law Gives the rate of flow of a fluid in a tube with a pressure difference P=P 1 -P 2 flow of Rate P P R V ) ( 2 1 4 L t 8 Example: A blood vessel is 0.1 m in length and has a radius of 1.5x10 -3 m. Blood flow at a rate of 1.0x10 -7 m 3 /s through this vessel. Determine the difference in pressure (in Pa) that must be maintained between the two ends of the vessel. ( =3x10 -3 N s/m 2 ) a) 5 4 12 R(P P) V b) 10 c) 15 d) 20 t 8L 73 3 2 V 1x10 m / s 8 3x10 N s / m (0.1m) t PP e) 25 4 4 3 R 3.14159 1.5x10 m 1 5 P a

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Zeroth Law of Thermodynamics If objects A and B are in thermal equilibrium with a third object, C, then A and B are in thermal equilibrium with each other. llows a definition of temperature Allows a definition of temperature
Different Temperature Scales Three different temperature scales are commonly in use: – Fahrenheit –C e l s i u s –K e l v i n Celsius define such that the freezing point of water is at a temperature of about 0 o C and boiling temperature is at about 100 o C.

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lecture17 - Physics 231 Lecture 17 Main points of todays...

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