小M asked in 科學其他:科學 · 1 decade ago

有關普通物理學的問題...

26.(a)As blood passes through the capillary bed in an organ,the capillaries join to form venules(small veins). If the blood velocity increases by a factor of 4.00 and the total cross-sectional area of the venules is 10.0 cm2,what is the total cross¬-sectional area of the capillaries feeding these venules?(b)How many capillaries are involved if their average diameter is 10.0 μm?

27.(a)What is the pressure drop due to the Bernoulli effect as water goes into a 3.00 cm diameter nozzle from a 9.00 cm diameter fire hose while carrying a flow of 40.0 L/s?(b)To what maximum height above the nozzle can this water rise?(The actual height will be significantly smaller due to air resistance.)

28.A glucose solution being administered with an IV has a flow rate of 4.00 cm3/min. What will the new flow rate be if the glucose is replaced by whole blood having the same density but a viscosity 2.50 times that of the glucose?All other factors remain constant.

29.The arterioles(small arteries)leading to an organ,such as the visual cortex of the brain,constrict in order to decrease flow to the organ. To essentially shut down an organ,blood flow is reduced to 1.00% of its original value. By what factor did the radii of the arterioles constrict?

30.Calculate the Reynolds numbers for flow in the hose and nozzle considered in Example 11. 2 to determine if the flow in either can possibly by laminar.

31.Oxygen reaches the veinless cornea of the eye by diffusing through its 0.500 mm thick tear layer. How long does it take the average oxygen molecule to do this?

1 Answer

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  • 1 decade ago
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    26. a)物質不滅 →blood流出venules=流進capillary

    V1*A1=V2*A2 → V1*10=4V1*A2 → A2= 2.5 cm²

    b) N*π*(5*10^--4)²= 2.5 → N= 3.18*10^6

    27. a) 物質不滅 → 流出直徑9的量=流進直徑3的量

    直徑9 cm時流速→ V*(9²π/4*10^-4)=40*10^-3→V=6.29 m/s

    同理直徑3 cm時流速=6.29*9=25.2 m/s

    Bernoulli’s equation :P +ρv²/2 +ρgh = C ;設大小口徑幾乎無高度差,不考慮ρgh

    ΔP=1000 kg/m³*(25.2²-6.29²)/2 m²/s²=2.98*10^5 NT/m²

    b) V²= 2gh→ 25.2²=2*9.8*h → h=32.4 m

    28.在低流速時,流速約略與黏度成反比

    血中葡萄糖流速=4/2.5=1.6 cm³/min

    29.流量減為1% → 面積減為1% → 截面半徑減為 1/10→ 收縮率為 10倍

    ps:題目很粗糙,實際情況沒那麼簡單

    30. Example 11. 2 在哪兒?

    31.氧分子要花多少時間才能靠擴散作用通過0.5mm的眼淚?

    抱歉,我沒概念!

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