Question

An air bubble of radius 5 mm rises through a vat of syrup at a steady rate. If the syrup has a density of 1.410³ kg/m³ and its viscosity is 20 kg/m-s, the rate of rise of the bubble is

• A. 5.8 mm/s
• B. 4.2 mm/s
• C. 3.8 mm/s
• D. 3.2 mm/s

Answer 1

Answer: (C)

3.8 mm/s

Answer 2

From equation, v = neglecting

density of air inside the bubble.

or, v = $\frac { 2 \times ( 0.005 ) ^ { 2 } \times 1.4 \times 10 ^ { 3 } \times 9.8 } { 9 \times 20 }$ = 3.8 mm/s