91. For a Newtonian fluid

1. 1. shear stress is proportional to shear strain

   
   
   

   2. rate of shear stress is proportional to shear strain

   
   
   

   3. shear stress is proportional to rate of shear strain

   
   
   

   4. rate of shear stress is proportional to rate of shear strain

   
   
   

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1. View Hint View Answer Discuss in Forum

   For a Newtonian fluid, shear stress is proportional to rate of shear strain.

   Correct Option: C

   For a Newtonian fluid, shear stress is proportional to rate of shear strain.

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92. Kaplan water turbine is commonly used when the flow through its runner is

1. 1. axial and the head available is more than 100 m

   
   
   

   2. axial and the head available is less than 10 m

   
   
   

   3. radial and the head available is more than 100 m

   
   
   

   4. mixed and the head available is about 50 m

   
   
   

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1. View Hint View Answer Discuss in Forum

   Kaplan turbine is an axial flow turbine and works at low heads (<50).

   Correct Option: B

   Kaplan turbine is an axial flow turbine and works at low heads (<50).

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93. In order to have maximum power from a Pelton turbine, the bucket speed must be

1. 1. equal to the jet speed

   
   
   

   2. equal to half of the jet speed

   
   
   

   3. equal to twice the jet speed

   
   
   

   4. independent of the jet speed

   
   
   

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1. View Hint View Answer Discuss in Forum

   For a pelton wheel, maximum power is obtained at,
   

   u =	υ
   	2

   Correct Option: B

   For a pelton wheel, maximum power is obtained at,
   

   u =	υ
   	2

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94. The velocity triangles at the inlet and exit of the rotor of a turbo machine are shown. V denotes the absolute velocity of the fluid, W denotes the relative velocity of the fluid and U denotes the blade velocity. Subscripts 1 and 2 refer to inlet and outlet respectively If V₂ = W₁ and V₁ = W₂, then the degree of reaction is
    

1. 1. 0

   
   
   

   2. 1

   
   
   

   3. 0.5

   
   
   

   4. 0.25

   
   
   

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1. View Hint View Answer Discuss in Forum

   DOR =	W2² −W1²
   	2/W2² −W1²

   
   

   =	1	= 0.5
   	2

   Correct Option: C

   DOR =	W2² −W1²
   	2/W2² −W1²

   
   

   =	1	= 0.5
   	2

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95. A hydraulic turbine develops 1000 kW power for a head of 40 m. If the head is reduced to 20 m, the power developed (in kW) is

1. 1. 177

   
   
   

   2. 354

   
   
   

   3. 500

   
   
   

   4. 707

   
   
   

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1. View Hint View Answer Discuss in Forum

   Pu =	P
   	H3/2

   
   

   ∴	P1	=	P2
   	H13/2		H23/2

   
   ⇒  P₂ = 353.55 kW.

   Correct Option: B

   Pu =	P
   	H3/2

   
   

   ∴	P1	=	P2
   	H13/2		H23/2

   
   ⇒  P₂ = 353.55 kW.

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