Question

A small metal ball of diameter 4 mm and density 10.5 g/cm³ is dropped in glycerine of density 1.5 g/cm³. The ball attains a terminal velocity of 8 cm/s, the coefficient of viscosity of glycerine is –

• A. 4.9 poise
• B. 9.8 poise
• C. 98 poise
• D. 980 poise

Answer 1

Answer: (B)

9.8 poise

Answer 2

$v_{T} = \frac{2}{9}\frac{r^{2}g}{\eta}(d_{b} - d_{e})$ Ž $\eta = \frac{2r^{2}g}{9v}(d_{b} - d_{e})$

= $\frac{2 \times 0.2 \times 0.2 \times 9 \times 980}{9 \times 8}$ = 9.8 poise