Then the body moves with a constant speed as net acceleration on the body is zero. A moment comes when the net upward force will be equal to net downward force as shown in the image(iii).(Since drag force is directly proportional to velocity) As body further moves down the velocity of the body increases and hence drag force will also increase. Considering the easy availability of water of required purity, the water is used as a primary standard of viscosity.What is the nature of the flow Flow through pipe: There are two types of fluid. As the body acquires some velocity, a drag force starts acting on the fluid upwards as shown in the image (ii). But still the net downward force would be greater as shown in the figure (ii). The coefficient of the viscosity of water at room temperature is 0.01 poise.Hence the body will accelerate downwards. Since the density of the body is more than density of the fluid, the net force will be downwards. Initially when the body is dropped, there are two forces acting on the body: a) force due to gravity F g and b) buoyancy force F B as shown in the image (i). The drag force is zero as the velocity of the body is zero.Let us study the subsequent motion of the body. Suppose a spherical object is dropped inside a container containing a certain fluid at time t=0 as shown in the figure(i). These data include the following: Density. Therefore the average pressure difference during the flow of water is P where Accurate thermophysical properties are available for several fluids. If ρ is the density of the liquid then the initial pressure difference between the ends of the tube is P 1 = h 1 ρ g and the final pressure difference P 2 = h 2 ρ g. If l and r are the length and radius of the capillary tube respectively, then If V is the volume between the two levels A and B, then volume of liquid flowing per second is t V .
The time taken for water level to fall from A to B is noted. The burette is filled with water and the pinch - stopper is removed. The capillary tube is kept horizontal as shown in figure. Determination of coefficient of viscosity of water by Poiseuille's flow method is as follows:Ī capillary tube of very fine bore is connected by means of a rubber tube to a burette kept vertically.
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