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Question
Water in canal, 6 m wide and 1.5 m deep, is flowing with a speed of 10 km/h. how much area will it irrigate in 30 minutes, if 8 cm of standing water is needed?
Solution
Consider an area of cross-section of canal as ABCD.
Area of cross-section = 6 × 1.5 = 9 m2
Speed of water = 10 km/h = 10000/60 metre/min
Volume of water that flows in 1 minute from canal = 9 x 10000/60 =1500 m3
Volume of water that flows in 30 minutes from canal = 30 × 1500 = 45000 m3
Let the irrigated area be A. Volume of water irrigating the required area will be equal to the volume of water that flowed in 30 minutes from the canal.
Vol. of water flowing in 30 minutes from canal = Vol. of water irrigating the reqd. area
4500 = (Ax8)/100
A = 562500 m2
Therefore, area irrigated in 30 minutes is 562500 m2.
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