7. A weakened blood vessel has stretched so that its diameter has become 20% lar

Question

7. A weakened blood vessel has stretched so that its diameter has become 20% larger. What is the velocity after stretching and what is the change in pressure? Assume a normal flow velocity of 0.4 m/s before stretching. (Phlond 1060 kg/m')? 8. A patient receives a saline solution from a bag through a needle. In order to decrease the rate at which the saline solution is delivered it is best to a. squeeze the bag b. use a larger gauge (smaller diameter) needle c. raise the height of the bag d. use a shorter needle 9. Diffusion is a result of a a pressure gradient in a fluid b. a temperature gradient in a fluid c) a concentration gradient in a fluid d. water being lighter than other molecules 10. The diffusion coefficient (constant) of sugar in water is of the order of 5x 10 m2/s. Estimate how long it would take for sugar to diffuse through a cup of coffee, 10 em long, the rate of mixing. if no other processes (such as convection or stirring) affected 11. The Zeroth Law of Thermodynamies tells us that a. Two systems, each in equilibrium with a third system, will be in equilibrium with each other b. Energy flows from a hot object to a cold object c. Objects get bigger when they are heated d. Ice floats on water 12. The temperature coefficient of linear expansion of steel is 12x10 *C. When the temperature increases from 5 °C to 25 °C, what is the increase in the length of a straight 25 m length of unclamped railway track?

Explanation / Answer

7. from the equation of continuity,

volume flow rate = A1 v1 = A2 v2

pi d1^2/ 4 v1 = pi d2^2 / 4 v2

d1^2 v1 = d2^2 v2

d1^2 (0.40) = (1.20 d1)^2 v2

v2 = 0.28 m/s .....Ans

from bernoulli's equation,

P1 +rho g h1 + rho v1^2 /2 = P2 + rho g h2 + rho v2^2 /2

h1 = h2

delta(P) = P2 - P1 = rho (v1^2 - v2^2)/2

= 1060 (0.4^2 - 0.28^2)/2

= 43.9 Pa

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