Water flows through two different pipes A and B of the same circular cross-section but at different flow rates

Q. Water flows through two different pipes A and B of the same circular cross-section but at different flow rates. The length of pipe A is 1.0 m and that of pipe B is 2.0 m. The flow in both the pipes is laminar and fully developed. If the frictional head loss across the length of the pipes is same, the ratio of volume flow rates QB   QA   is______________(round off to two decimal places).

Ans: 0.5

Sol: