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

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

$v^{\prime}=4 v$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

A wheel having moment of inertia $2 \,kg \cdot m ^{2}$ about its vertical axis, rotates at the rate of $60\, rpm$ about this axis. The torque which can stop the wheel's rotation in one minute would be
Find the gravitational force of attraction between a particle of mass m and a uniform slender rod of mass M and length L for the two orientations shown in the figure.
The linear momentum $p$ of a body of mass $5 \,kg$ varies with time $t$ as, $p = 5t^2 + t + 5$ It follows that the body is moving with
Given below are two statements: One is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.

Assertion $(A)$:The stretching of a spring is determined by the shear modulus of the material of the spring.

Reason $(R)$:A coil spring of copper has more tensile strength than a steel spring of same dimensions.

In the light of the above statements, choose the most appropriate answer from the options given below:

A mass $m$ hangs with the help of a string wrapped around a pulley on a frictionless bearing. The pulley has mass m and radius $R$. Assuming pulley to be a perfect uniform circular disc, the acceleration of the mass $m$, if the string does not slip on the pulley, is
In terms of basic units of mass $(M)$, length $(L)$, time $(T)$ and charge $(Q)$, the dimensions of magnetic permeability of vacuum $\left(\mu_0\right)$ would be
There are two particles $P$ and $Q$ separated by distance $10\ km$ and moving with velocities $10\ kmph$ as shown on a smooth horizontal surface. The time elapsed before they come at minimum separation is.........$hr$
One mole of an ideal gas at $STP$ is heated in an insulated closed container until the average speed of its molecules is doubled. Its pressure would therefore increase by factor.
There are three arrangement of three point masses (each of mass $m$). In which of the following three arrangements they are arranged in order of increasing magnitude of gravitational force on point mass marked as $1$ ?
Let $I_1, I_2$ and $I_3$ be the moment of inertia of a uniform square plate about axes $AOC, xDx'$ and $yBy'$ respectively as shown in the figure. The moments of inertia of the plate $I_1 : I_2 : I_3$ are in the ratio.