An iron sphere of diameter 10 mm falls through a column of oil of density `940 kg//m^(3)` . The density of iron is. `7.8 xx 10^(3) kg//m^(3)`. The coefficient of viscosity of oll is` 4.48 Ns//m^(2)`. Caleulate the terminal velocity attained by the ball.

Explanation

Radius of the bail = ` a = 5 xx 10 ^(-3) m `
Density of oil `= sigma = 940 kg//m^(3) `
Density of iron sphere = ` rho = 7.8 xx 10 ^(3) kg//m^(3)`
Coefficient of viscosity of oil =` eta = 4.78 Ns//m^(2)`
Terminal velocity `= v= ? `
` " " v= (2(rho - sigma)a^(2) g)/( 9eta ) = ( 2(7.8 xx 10 ^(3) -940)xx 25xx 10 ^(-6) xx 9.8)/( 9xx 4. 78) `
` " " = 0.078 m//s `