The terminal velocity of a copper ball of radius 1.0 mm falling through a tank of oil at 20^(@)C is 8.5cms^(-1) .Compute the viscosity of the oil at 20^(@)C .Density of oil is 1.5xx10^(3)kgm^(-3) , density of copper is 8.9xx10^(3)kgm^(-3)

The terminal velocity of a copper ball of radius 1.0 mm falling throug

1.	The terminal velocity of a copper ball of radius 1.0 mm falling through a tank of oil at 20^(@)C is 8.5cms^(-1) .Compute the viscosity of the oil at 20^(@)C .Density of oil is 1.5xx10^(3)kgm^(-3) , density of copper is 8.9xx10^(3)kgm^(-3)
Answer» SOLUTION :RADIUS of COPPER ball , `r=2.0mm=2xx10^(-3)m` The TERMINAL velocity of ball , `v_(t)=6.5cms^(-1)=6.5xx10^(-2)ms^(-1)` Density of oil `sigma=1.5xx10^(3)kgm^(-3)` Density of copper `rho=8.9xx10^(3)kgm^(-3)` From Stoke.s law , `eta=(2)/(9)xx(r^(2)g)/(v_(t))(rho-sigma)` `=(2xx(2xx10^(-3))^(2)xx9.8(8.9xx10^(3)-1.5xx10^(3)))/(9xx6.5xx10^(-2))` `=9.917xx10^(-6+3+2)` `=9.9xx10^(-1)` `=0.99kgm^(9-1)s^(-1)`