KVPY SA Exam 19-Nov-2017 Question Paper

Question : 28 of 80

Marks: +1, -0

The bhagirathi and the Alaknanda merge at Deoprayag to form the Ganga with their speeds in the ratio 1 :1.5. The cross-sectional areas of the Bhagirathi, the Alaknanda and the Ganga are in the ratio 1 : 2 :3. Assuming stremline flow, the ratio of the speed of Ganga to that of the Alaknands is

7 : 9
4 :3
8 : 9
5 :3

Validate

Solution:

By equation of continuity
Area of Bhagirathi ⇒ A
Area of Alaknanda ⇒ 2A
Area of Ganga ⇒ 3A

V_B : V_\AL : V_G : ⇒ V : 3/2 V : V_1

By equation of continuity

AV +3/2A.2V⇒3A.V_1

V_\ganga = 4/3V

V_\Alaknanda /V_\ganga⇒{3/2V}/{4/3V}=9/8

V_\ganga : V_\Alaknanda = 8 : 9

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