Question

An ideal fluid flows through a pipe of circular cross-section made of two sections with diameters 2.5 cm and 3.75 cm. The ratio of the velocities in the two pipes is

• A. 9 : 4
• B. 3 : 2
• C. $\sqrt { 3 } : \sqrt { 2 }$
• D.

Answer 1

Answer: (A)

9 : 4

Answer 2

According to equation of continuity

Or $\frac { \mathrm { v } _ { 1 } } { \mathrm { v } _ { 2 } } = \frac { \mathrm { a } _ { 2 } } { \mathrm { a } _ { 1 } } = \frac { \pi \mathrm { d } _ { 2 } ^ { 2 } / 4 } { \pi \mathrm {~d} _ { 1 } ^ { 2 } / 4 } = \left( \frac { \mathrm { d } _ { 2 } } { \mathrm {~d} _ { 1 } } \right) ^ { 2 } = \left( \frac { 3.75 } { 2.50 } \right) ^ { 2 } = \frac { 9 } { 4 }$