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ISRO 2009 Mechanical Engineering Questions, Answers and Explanation

ISRO 2009 Mechanical Engineering Questions, Answers and Explanation

2. If the stream function of a two dimensional flow is Ψ = 3xy, then the velocity at a point (2,3) is
a) 7.21 unit
b) 18 unit
c) 10.82 unit
d) 54 unit

Answer
c) 10.82 unit

Explanation[Fluid Mechanics]
u = ∂ Ψ/∂ y = 3x
v =- ∂ Ψ/∂ x = -3y
At (2,3), u = 3x2 = 6 unit
At (2,3), v = -3x3 = -9 unit
Resultant velocity = √(62+(-9)2)= √(117)=3√(13)=10.81 unit

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