10 Questions
1 kgf = 9.81N, hence 1kgf-sec/m2 = 9.81N-sec/m2 but 1N = force = mass x acceleration= kg-sec2/m = 1000g-sec2/100cm =10g-sec2/cm = 10 dyne hence 1kgf-sec/m2 = 9.81Nsec/m2= 98.1 dyne-sec/cm2 = 98.1 poise
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viscosity = shear stress/(change in velocity/ change in distance) = (shear stress x change in distance)/change in velocity = (shear stress x change in distance)/ (distance/time) = (shear stress x distance x time)/ distance = shear stress x time = ( force/Area) x time = (force x time)/Area , by putting cgs unit of force = dyne, area = cm2, time= sec ,, we get viscosity = (dyne-sec)/cm2
as we know viscosity = shear stress/ unit rate of strain = shear stress/ change in velocity/ change in distance = ((force/area) x change in distance)/ change in velocity = (force x distance)/ ((areax distance)/time)= (force, as we know in mks system force is denoted by kgf, distance with meter (m), area with m2, time with sec we get Viscosity in mks = kgf-m/(m3/sec) = kgf-sec/m2
has we know that top layer of fluids caused shear stress on adjacent lower layer while the lower layer causes shear stress on top adjacent layer. This shear stress is directly proportional to the rate of change of velocity with respect to distance between layer say y. hence shear stress ∠du/dy, where u = velocity of flow, y =distance of adjacent layer, also du/dy = rate of change of velocity with respect to y shear stress = μ du/dy where μ = shear stress/ (du/dy) = viscosity
density = specific gravity x density of water = 0.7x 1000 = 700kg/cum specific weight = 9.81 x density = 9.81 x 700 = 6867N/cum weight = volume of liquid x specific weight = 6867 x .001 =6.867N
1- specific weight = weight/volume = 7N/(1/1000)cum = 7000 N/cum 2- density = specific weight / acc due to gravity = 7000 / 9.81 = 713.5kg/cum 3- specific gravity = specific weight of liquid/ specific weight of water = 713.5/1000 = 0.7135
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