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To pump liquid out of a vessel which is not wetted by it into a vessel wetted by it one may make use of surface tension forces (a capillary pump). What will be the speed of flow of petrol in a capillary of 2 mm diameter and of 10 cm length? The experiment is conducted in conditions of weightlessness. |
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Answer» Solution :TWO FORCES act on a fluid in conditions of weightlessness: the force of surface tension sur rod and the force of hydraulic resistance `F_(res)= lambda(l)/(d)*(rho v^(2))/(2)*(pi d^(2))/(4)` (see 20.17) SINCE the velocity of the fluid is small, for small Reynolds numbers `lambda=(64)/(Re)=(64 eta)/(rho vd)`. EQUATING the forces, we obtain after some simplifications. `v= sigma d//8 eta l` Compute the velocity to find the Reynolds nurober, and make sure that it is much less than 2320. |
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