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STD 11 - 9.1 , fluid mechanics — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 11 - 9.1 , fluid mechanics4 Marks
MCQ
An incompressible fluid flows steadily through a cylindrical pipe which has radius $2r$ at point $A $ and radius $r $ at $B $ further along the flow direction. If the velocity at point $A$  is $v, $ its velocity at point $B$  is
  • A
    $2v$
  • B
    $v$ 
  • C
    $v/2$
  • ✓
    $4v$
✓

Answer

Correct option: D.
$4v$
d
(d) From equation of continuity volume of water entering per second at $\mathrm{A}=$ volume of water exiting per second from $B$

Let $v$ be the velocity at point $B$, then

$\pi(2 R)^{2} v=\pi\left(R^{2}\right) v^{\prime}$

$v^{\prime}=4 v$

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