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The velocity profile of a fully developed laminar flow in a straight circular pipe, as shown in the figure, is given by the expression
u(r) = − R² 
∂p 

1 − r² 
4μ ∂x R²
where ∂p/∂x is a constant
The average velocity of fluid in the pipe is
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− R² 
∂p 
8μ ∂x -
− R² 
∂p 
4μ ∂x -
− R² 
∂p 
2μ ∂x -
− R² 
∂p 
μ ∂x
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Correct Option: A

| u = − | ![]() | − | ![]() | ![]() | 1 − | ![]() | |||
| 4μ | dx | R |
dQ =u (2πrdr)

Solving, we get
| Q = − | ![]() | − | ![]() | ||
| 8μ | dx |
Now Q = Area ´ average velocity
| ∴ uav = | = | ||
| Area | πR2 |
| or uav = | ![]() | ![]() | ||
| 8μ | dx |