Objective Physics for NEET

Abhay Kumar

Chapter 10

Fluid Mechanics - all with Video Answers

Educators

Chapter Questions

Problem 1

When $n$ fluids of masses $m_{1}, m_{2}, \ldots, m_{n}$ and densities $\rho_{1}$, $\rho_{2}, \ldots, \rho_{n}$ respectively are mixed together, then resultant density of mixture is
(a) $\frac{\sum_{i=1}^{n} m_{i}}{\sum_{i=1}^{n} \rho_{i}}$
(b) $\frac{\sum_{i=1}^{n} m_{i} \rho_{i}}{\sum_{i=1}^{n} m_{i}}$
(c) $\frac{\sum_{i=1}^{n} m_{i}}{\sum_{i=1}^{n} \frac{m_{i}}{\rho_{i}}}$
(d) infinity

Mahendra K

Mahendra K

Numerade Educator

Problem 2

Two bodies are in equilibrium when suspended in water from the arms of a balance. The mass of one body is $36 \mathrm{~g}$ and its density is $9 \mathrm{~g} / \mathrm{cm}^{3}$. If the mass of the other is $48 \mathrm{~g}$, its density in $\mathrm{g} / \mathrm{cm}^{3}$ is
(a) $\frac{4}{3}$
(b) $\frac{3}{2}$
(c) 3
(d) 5

Mahendra K

Numerade Educator

Problem 3

A wooden block with a coin placed on its top, floats in water as shown in the figure. The distance $l$ and $h$ are shown in figure. After some time the coin falls into the water. Then
(a) $l$ decreases and $h$ increases
(b) $l$ increases and $h$ decreases
(c) both $l$ and $h$ increase
(d) both $l$ and $h$ decrease

Mahendra Kumar

Numerade Educator

Problem 4

If the weight of a body in vacuum is $w$ and $w_{1}$ and $w_{2}$ are weights when it is immersed in liquids of specific gravities $\rho_{1}$ and $\rho_{2}$ respectively, then the relation among $w, w_{1}$ and $w_{2}$ is
(a) $w=\frac{w_{1} \rho_{2}+w_{2} \rho_{1}}{w_{1}+w_{2}}$
(b) $w=\frac{w_{1} \rho_{2}-w_{2} \rho_{1}}{\rho_{2}-\rho_{1}}$
(c) $w=\frac{w_{1} \rho_{1}+w_{2} \rho_{2}}{\rho_{1}+\rho_{2}}$
(d) $w=\frac{w_{1} \rho_{2}+w_{2} \rho_{1}}{\rho_{1}+\rho_{2}}$

Mahendra K

Numerade Educator

Problem 5

When equal volumes of two substances are mixed, the specific gravity of mixture is $4 .$ When equal weights of the same substances are mixed, the specific gravity of the mixture is $3 .$ The specific gravity of the two substances would be
(a) 6 and 2
(b) 3 and 4
(c) $2.5$ and $3.5$
(d) 5 and 3

Mahendra K

Numerade Educator

Problem 6

A liquid of density $\rho$ is completely filled in a rectangular box. The box is accelerating horizontally with acceleration $a$. What should be the gauge pressure at four points $P, Q, R, S ?$
(a) $P_{P}=0, P_{Q}=0, P_{R}=\rho g h, P_{S}=0$
(b) $P_{P}=\rho g h, P_{o}=0, P_{k}=\rho g a, P_{s}=\rho a L$
(c) $P_{P}=0, P_{Q}=\rho g h, P_{k}=\rho g h+\rho a L, P_{S}=\rho a L$
(d) $P_{P}=\rho g h, P_{\varrho}=0, P_{R}=\rho g h-\rho a L, P_{s}=\rho g L$

Mahendra K

Numerade Educator

Problem 7

A closed rectangular tank is completely filled with water and is accelerated horizontally with an acceleration a towards right. Pressure is (i) maximum at, and
(ii) minimum at
(a) (i) $B$ (ii) $D$
(b) (i) $C$ (ii) $D$
(c) (i) $B$ (ii) $C$
(d) (i) $B$ (ii) $A$

Mahendra K

Numerade Educator

Problem 8

A body of density $d$ is counterpoised by $M g$ of weights of density $d_{2}$ in air of density $d$. Then the true mass of the body is
(a) $M$
(b) $M\left(1-\frac{d}{d_{2}}\right)$
(c) $M\left(1-\frac{d}{d_{1}}\right)$
(d) $\frac{M\left(1-d / d_{2}\right)}{\left(1-d / d_{1}\right)}$

Mahendra K

Numerade Educator

Problem 9

A ball whose density is $0.4 \times 10^{3} \mathrm{~kg} / \mathrm{m}^{3}$ falls into water from a height of $9 \mathrm{~cm}$. To what depth does the ball sink?
(a) $9 \mathrm{~cm}$
(b) $6 \mathrm{~cm}$
(c) $4.5 \mathrm{~cm}$
(d) $2.25 \mathrm{~cm}$

Mahendra K

Numerade Educator

Problem 10

A wooden ball of density $D$ is immersed in water of density $d$ to a depth $h$ below the surface of water and then released. Upto what height will the ball jump out of water?
(a) $\frac{d}{D} h$
(b) $\left(\frac{d}{D}-1\right) h$
(c) $h$
(d) Zero

Mahendra K

Numerade Educator

Problem 11

A spherical ball of radius $r$ and relative density $0.5$ is floating in equilibrium in water with half of it immersed in water. The work done in pushing the ball down so that whole of it is just immersed in water is (where $\rho$ is the density of water)
(a) $\frac{5}{12} \pi r^{4} \rho g$
(b) $0.5 \rho r g$
(c) $\frac{4}{3} \pi r^{3} \rho g$
(d) $\frac{2}{3} \pi r^{4} \rho g$

Mahendra K

Numerade Educator

Problem 12

Block $A$ in the figure shown here hangs by a cord from dynamometer (spring balance) $D_{1}$ and is submerged in a liquid $C$ contained in a beaker $B$. The mass of the beaker is $1 \mathrm{~kg}$ and the mass of liquid is $1.5 \mathrm{~kg}$. The readings of dynamometers $D_{1}$ and $D_{2}$ are $2.5 \mathrm{~kg}$ and $7.5 \mathrm{~kg}$ respectively. What will be the readings of $D_{1}$ and $D_{2}$ if block $A$ is pulled up out of liquid?
(a) $D$, will read $5 \mathrm{~kg}$ and $D_{2}$ will also read $5 \mathrm{~kg}$
(b) $D$ will read $7.5 \mathrm{~kg}$ and $D_{2}$ will read $2.5 \mathrm{~kg}$
(c) $D_{1}$ will read $2.5 \mathrm{~kg}$ and $D_{2}$ will read $7.5 \mathrm{~kg}$
(d) $D_{1}$ will read $10 \mathrm{~kg}$ and $D_{2}$ will read $2.5 \mathrm{~kg}$

Mahendra K

Numerade Educator

Problem 13

A homogeneous solid cylinder of length $L(L<H / 2)$, cross-sectional area $\frac{A}{5}$ is immersed such that it floats with its axis vertical at the liquid-liquid interface with length $\frac{L}{4}$ in the denser liquid as shown in the figure. The lower density liquid is open to atmosphere having pressure $P_{a}$. Then density $D$ of solid is given by
(a) $\frac{5}{4} d$
(b) $\frac{4}{5} d$
(c) $\bar{d}$
(d) $\frac{d}{5}$

Mahendra K

Numerade Educator

Problem 14

In making an alloy, a substance of specific gravity $s_{1}$ and mass $m_{1}$ is mixed with another substance of specific gravity $s_{2}$ and mass $m_{2} ;$ then the specific gravity of the alloy is
(a) $\left(\frac{m_{1}+m_{2}}{s_{1}+s_{2}}\right)$
(b) $\left(\frac{s_{1} s_{2}}{m_{1}+m_{2}}\right)$
(c) $\left(\frac{m_{1}+m_{2}}{\frac{m_{1}}{s_{1}}+\frac{m_{2}}{s_{2}}}\right)$
(d) $\left(\frac{\frac{m_{1}}{s_{1}}+\underline{m_{2}}}{m_{1}+m_{2}}\right)$

Mahendra K

Numerade Educator

Problem 15

A wooden block is floating in a water tank. The block is pressed to its bottom. During the process, work done is equal to
(a) work done against upthrust exerted by the water.
(b) work done against upthrust plus loss of gravitational potential energy of the block.
(c) work done against upthrust minus loss of gravitational potential energy of the block.
(d) None of these.

Mahendra K

Numerade Educator

Problem 16

A closed vessel is half-filled with water. There is a hole near the top of the vessel and air is pumped out from this hole
(a) the water level will rise up in the vessel.
(b) the pressure at the surface of water will decrease.
(c) the force exerted due to the water on the bottom of the vessel will decrease.
(d) the density of the liquid will decrease.

Mahendra K

Numerade Educator

Problem 17

When at rest, a liquid stands at the same level in the tubes shown in figure. But as indicated a height difference $h$ occurs when the system is given an acceleration a towards the right. Here, $h$ is equal to
(a) $\frac{a L}{2 g}$
(b) $\frac{g L}{2 a}$
(c) $\frac{g L}{a}$
(d) $\frac{a L}{g}$

Mahendra K

Numerade Educator

Problem 18

A cart supports a cubic tank filled with a liquid upto the top. The cart moves with a constant acceleration a in the horizontal direction. The tank is tightly closed. Assume that the lid does not exert any pressure on the liquid when in motion with uniform acceleration. The pressure at a point at a depth $h$ and distance $l$ from the front wall is
(a) $d g h$
(b) dla
(c) $d g h+d l a$
(d) $d g h-d l a$

Mahendra K

Numerade Educator

Problem 19

A piece of metal floats on $\mathrm{Hg}$. The coefficient of expansion of metal and $H g$ are $Y_{1}$ and $Y_{2}$ respectively. If the temperature of both $\mathrm{Hg}$ and metal are increased by an amount $\Delta T$, by what factor the fraction of the volume of metal submerged in mercury changes?
(a) $\left(\gamma_{2}-\gamma_{1}\right) \Delta T$
(b) $\left(\frac{\gamma_{2}+\gamma_{1}}{2}\right) \Delta T$
(c) $\left(\frac{2 \gamma_{1} \gamma_{2}}{\gamma_{1}+\gamma_{2}}\right) \Delta T$
(d) $\left(\frac{\gamma_{1} \gamma_{2}}{\gamma_{1}+\gamma_{2}}\right) \Delta T$

Mahendra K

Numerade Educator

Problem 20

A vessel contains oil (density $=0.8 \mathrm{gm} / \mathrm{cm}^{3}$ ) over mercury (density $\left.=13.6 \mathrm{~g} / \mathrm{cm}^{3}\right)$. A homogeneous sphere floats with half of its immersed in mercury and the other half in oil. The density of the material of the sphere in $\mathrm{g} / \mathrm{cm}^{3}$ is
(a) $3.3$
(b) $6.4$
(c) $7.2$
(d) $12.8$

Mahendra K

Numerade Educator

Problem 21

An astronaut is standing at the north pole of a newly discovered planet of radius $R .$ He holds a container full of liquid having mass $m$ and volume $V .$ At the surface of the liquid pressure is $P_{e}$ and at a depth $d$ below the surface, pressure is $P$. From this information determine the mass of the planet
(a) $\frac{\left(P+P_{0}\right) V R^{2}}{G d m}$
(b) $\frac{\left(P+P_{0}\right) R^{2} V}{2 G d m}$
(c) $\frac{\left(P-P_{0}\right) R^{2} V}{2 G d m}$
(d) $\frac{\left(P-P_{0}\right) R^{2} V}{G d m}$

Mahendra K

Numerade Educator

Problem 22

A U-tube containing a liquid is accelerated horizontally with a constant acceleration $a .$ If the separation between the two vertical limbs is $l$, then the difference in the heights of the liquid in the two arms is
(a) zero
(b) $l$
(c) $\frac{l a}{g}$
(d) $\frac{l a}{g}$

Mahendra K

Numerade Educator

Problem 23

Three liquids having densities $\rho_{1}, \rho_{2}$ and $\rho_{3}$ are filled in
a U-tube. Length of each liquid column is equal to l. $\rho_{\text {. }}$ $>\rho_{2}>\rho_{3}$ and liquids remain at rest (relative to the tube) in the position shown in figure. It is possible that
(a) U-tube is accelerating leftwards
(b) U-tube is accelerating upwards with acceleration $g$
(c) U-tube is moving with a constant velocity
(d) None of these

Mahendra K

Numerade Educator

Problem 24

A ball floats on the surface of water in a container exposed to the atmosphere. Will the ball remain immersed at its former depth or will it sink or will it rise if the container is covered and the air is removed?
(a) The ball sinks
(b) The ball rises
(c) The ball remains immersed at its former depth
(d) It oscillates

Mahendra K

Numerade Educator

Problem 25

A vessel of water is placed on the floor of an elevator. How does the pressure at the bottom of the vessel change if the elevator moves up with uniform acceleration $a$ ?
(a) Increases by h\rhoa
(b) Decreases by $h \rho a$
(c) No change in pressure
(d) None of these

Mahendra K

Numerade Educator

Problem 26

A cube of mass $m$ and density $D$ is suspended from the point $P$ by a spring of stiffness $K .$ The system is kept inside a beaker filled with a liquid of density $d$. The elongation in the spring, assuming $D>d$, is
(a) $\frac{m g}{K}\left(1-\frac{d}{D}\right)$
(b) $\frac{m g}{K}\left(1-\frac{D}{d}\right)$
(c) $\frac{m g}{K}\left(1+\frac{d}{D}\right)$
(d) None of these

Mahendra K

Numerade Educator

Problem 27

A piece of wood is floating in water. When the temperature of water rises, the apparent weight of the wood will
(a) increase
(b) decrease
(c) may increases or decrease
(d) remain same

Akshaya Rs

Numerade Educator

Problem 28

A body floats in water with one-third of its volume above the surface of water. If it is placed in oil, it floats with half of its volume above the surface of the oil. The specific gravity of the oil is
(a) $\frac{5}{3}$
(b) $\frac{4}{3}$
(c) $\frac{3}{2}$
(d) 1

Ashok Prajapati

Ashok Prajapati

Numerade Educator

Problem 29

The profile of advancing liquid in a tube is a
(a) straight line
(b) circle
(c) parabola
(d) hyperbola

Mahendra K

Numerade Educator

Problem 30

The density $(\rho)$ of atmospheric air varies with height $(h)$ above the ground according to the relation $\rho=\rho_{0} e^{-\lambda h}$ where $\lambda$ is a constant. At what height above the ground is the pressure half its value on the surface?
(a) $\frac{2}{\lambda}$
(b) $\frac{1}{\lambda}$
(c) $\frac{\ln 2}{\lambda}$
(d) $2 \frac{\ln 2}{\lambda}$

Mahendra K

Numerade Educator

Problem 31

A jar is filled with two non-mixing liquids 1 and 2 having densities $\rho_{1}$ and $\rho_{2}$ respectively. A solid ball, made of a material of density $\rho_{3}$, is dropped in the jar. It comes equilibrium in the position shown in the figure. Which of the following is true for $\rho_{1}, \rho_{2}$ and $\rho_{3} ?$
(a) $\rho_{3}<\rho_{1}<\rho_{2}$
(b) $\rho_{1}>\rho_{3}<\rho_{2}$
(c) $\rho_{1}<\rho_{2}<\rho_{3}$
(d) $\rho_{1}<\rho_{3}<\rho_{2}$

Mahendra K

Numerade Educator

Problem 32

In which one of the following cases will the liquid flow in a pipe be most streamlined?
(a) Liquid of high viscosity and high density flowing through a pipe of small radius
(b) Liquid of high viscosity and low density flowing through a pipe of small radius
(c) Liquid of low viscosity and low density flowing through a pipe of large radius
(d) Liquid of low viscosity and high density flowing through a pipe of large radius

Mahendra K

Numerade Educator

Problem 33

A tank is filled with water upto a height $H$. Water is allowed to come out of a hole $P$ in one of the walls at a depth $D$ below the surface of water. Express the horizontal distance $x$ in terms of $H$ and $D$
(a) $x=\sqrt{D(H-D)}$
(b) $x=\sqrt{\frac{D(H-D)}{2}}$
(c) $x=2 \sqrt{D(H-D)}$
(d) $x=4 \sqrt{D(H-D)}$

Mahendra K

Numerade Educator

Problem 34

There is a hole in the bottom of tank having water. If total pressure at bottom is $3 \mathrm{~atm}\left(1 \mathrm{~atm}=10^{5} \mathrm{~N} / \mathrm{m}^{2}\right)$,
then the velocity of water flowing from hole is
(a) $\sqrt{400} \mathrm{~m} / \mathrm{s}$
(b) $\sqrt{600} \mathrm{~m} / \mathrm{s}$
(c) $\sqrt{60} \mathrm{~m} / \mathrm{s}$
(d) None of these

Mahendra K

Numerade Educator

Problem 35

As shown in the following figure, water squirts horizontally out of two small holes in the side of the cylinder and the two streams strike the ground at the same point. If the hole $Q$ is at a height h above the ground and the level of water stands at height $H$ above the ground, then the height of $P$ above ground level is
(a) $2 h$
(b) $\mathrm{H} / \mathrm{h}$
(c) $H-h$
(d) $\mathrm{H} / \mathrm{2}$

Mahendra K

Numerade Educator

Problem 36

If $A$ denotes the area of free surface of a liquid and $h$ the depth of an orifice of area of cross-section $a$, below the liquid surface, then the velocity $v$ of flow through the orifice is given by
(a) $v=\sqrt{2 g h}$
(b) $v=\sqrt{2 g h} \sqrt{\left(\frac{A^{2}}{A^{2}-a^{2}}\right)}$
(c) $v=\sqrt{2 g h} \sqrt{\left(\frac{A}{A-a}\right)}$
(d) $v=\sqrt{2 g h} \sqrt{\left(\frac{A^{2}-a^{2}}{A^{2}}\right)}$

Mahendra K

Numerade Educator

Problem 37

A cylinder containing water stands on a table of height $H$. A small hole is punched in the side of cylinder at its base. The stream of water strikes the ground at a horizontal distance $R$ from the table. Then the depth of water in the cylinder is
(a) $\vec{H}$
(b) $R$
(c) $\sqrt{R H}$
(d) $R^{2} / 4 H$

Mahendra K

Numerade Educator

Problem 38

Two rain drops reach the earth with different terminal velocities having ratio $9: 4$. Then the ratio of their volumes is
(a) $3: 2$
(b) $4: 9$
(c) $9: 4$
(d) $27: 8$

Mahendra K

Numerade Educator

Problem 39

A large tank is filled with water to a height $H .$ A small hole is made at the base of the tank. It takes $T_{1}$ time to decrease the height of water to $\frac{H}{\eta}(\eta>1)$; and it takes $T_{2}$ time to take out the rest of water. If $T_{1}=T_{2}$, then the value of $\eta$ is
(a) 2
(b) 3
(c) 4
(d) $2 \sqrt{2}$

Mahendra K

Numerade Educator

Problem 40

The L-shaped glass tube is just immersed in flowing water such that its opening is pointing against flowing water. If the speed of water current is $v$, then
(a) the water in the tube rises to height $\frac{v^{2}}{2 g}$
(b) the water in the tube rises to height $\frac{g}{2 v^{2}}$
(c) the water in the tube does not rise at all
(d) None of these

Ashok Prajapati

Ashok Prajapati

Numerade Educator

Problem 41

Two capillaries of same length and radii in the ratio $1: 2$ are connected in series. A liquid flows through then in streamlined condition. If the pressure across the two extreme ends of the combination in $1 \mathrm{~m}$ of water, the pressure difference across first capillary is
(a) $9.4 \mathrm{~m}$
(b) $4.9 \mathrm{~m}$
(c) $0.49 \mathrm{~m}$
(d) $0.94 \mathrm{~m}$

Mahendra K

Numerade Educator

Problem 42

Two capillaries of length $L$ and $2 L$ and of radius $R$ and $2 R$ are connected in series. The net rate of flow of fluid through them will be (Given rate of the flow through single capillary, $\left.X=\frac{\pi P R^{2}}{8 \eta L}\right)$
(a) $\frac{8}{9} X$
(b) $\frac{9}{8} X$
(c) $\frac{5}{7} X$
(d) $\frac{7}{5} X$

Mahendra K

Numerade Educator

Problem 43

Three capillaries of length $L, L / 2$ and $L / 3$ are connected in series. Their radii are $r, r / 2$ and $r / 3$ respectively. Then if stream-line flow is to be maintained and the pressure across the first capillary is $P$, then
(a) the pressure difference across the ends of second capillary is $8 P$
(b) the pressure difference across the third capillary is $43 P$
(c) the pressure difference across the ends of the second capillary is $16 P$
(d) the pressure difference across the third capillary is $59 P$

Mahendra K

Numerade Educator

Problem 44

A large open tank has two holes in the walls. One is a square hole of side $L$ at a depth $y$ from the top and other is a circular hole of radius $R$ at a depth $4 y$ from the top. When the tank is completely filled with water the quantities of water flowing out per second from both the holes are the same. Then $R$ is equal to
(a) $2 \pi L$
(b) $\frac{L}{\sqrt{2 \pi}}$
(c) $L$
(d) $\frac{L}{2 \pi}$

Mahendra K

Numerade Educator

Problem 45

A tank is filled upto a height $h$ with a liquid and is placed on a platform of height $h$ from the ground. To get maximum range $x_{m}$, a small hole is punched at a distance of $y$ from the free surface of the liquid. Then
(a) $x_{m}=2 h$
(b) $x_{m}=1.5 h$
(c) $y=2 h$
(d) $y=0.75 h$

Mahendra K

Numerade Educator

Problem 46

A cylindrical tank has a hole of $1 \mathrm{~cm}^{2}$ in its bottom. If the water is allowed to flow into the tank from a tube above it at the rate of $70 \mathrm{~cm}^{3} / \mathrm{s}$ then the maximum height upto which water can rise in the tank is
(a) $2.5 \mathrm{~cm}$
(b) $5 \mathrm{~cm}$
(c) $10 \mathrm{~cm}$
(d) $0.25 \mathrm{~cm}$

Mahendra K

Numerade Educator

Problem 47

A large tank filled with water to a height of $h$ is said to be emptied through a small hole at the bottom. The ratio of time taken for the level of water to fall down from $h$ to $h / 2$ and from $h / 2$ to zero is
(a) $\sqrt{2}$
(b) $1 / \sqrt{2}$
(c) $\sqrt{2}-1$
(d) $\frac{1}{\sqrt{2}-1}$

Mahendra K

Numerade Educator

Problem 48

A cylindrical vessel contains a liquid of density $\rho$ upto a height $h$. The liquid is closed by a piston of mass $m$ and area of cross-section $A$. There is a small hole at the bottom of the vessel. The speed $v$ with which the liquid comes out of the hole is
(a) $\sqrt{2 g h}$
(b) $\sqrt{2\left(g h+\frac{m g}{\rho A}\right)}$
(c) $\sqrt{2\left(g h+\frac{m g}{A}\right)}$
(d) $\sqrt{2 g h+\frac{m g}{A}}$

Mahendra K

Numerade Educator

Problem 49

Equal volumes of two immiscible liquids of densities $\rho$ and $2 \rho$ are filled in a vessel as shown in figure. Two small holes are punched at depth $h / 2$ and $3 h / 2$ from the surface of lighter liquid. If $v_{1}$ and $v_{2}$ are the velocities of efflux at these two holes, then $v_{1} / v_{2}$ is
(a) $\frac{1}{2 \sqrt{2}}$
(b) $\frac{1}{2}$
(c) $\frac{1}{4}$
(d) $\frac{1}{\sqrt{2}}$

Mahendra K

Numerade Educator

Problem 50

A gas flows with a velocity $v$ along a pipe of cross-sectional area $S$ and bent an angle of $90^{\circ}$ at a point $A .$ What force does the gas exert on the pipe at $A$ if its density is $\rho$ ?
(a) $\frac{\sqrt{2} S v}{\rho}$
(b) $\sqrt{2} S v^{2} \rho$
(c) $\frac{\sqrt{3} S v^{2} \rho}{2}$
(d) $\sqrt{3} S v^{2} \rho$

Mahendra K

Numerade Educator

Problem 51

At what speed, the velocity head of water is equal to pressure head of $40 \mathrm{~cm}$ of $\mathrm{Hg}$ ?
(a) $10.3 \mathrm{~m} / \mathrm{s}$
(b) $2.8 \mathrm{~m} / \mathrm{s}$
(c) $5.6 \mathrm{~m} / \mathrm{s}$
(d) $8.4 \mathrm{~m} / \mathrm{s}$

Ashok Prajapati

Ashok Prajapati

Numerade Educator

Problem 52

A capillary tube is attached horizontally to a constant head arrangement. If the radius of the capillary tube is increased by $10 \%$, then the rate of flow of liquid will change nearly by
(a) $+10 \%$
(b) $+46 \%$
(c) $-10 \%$
(d) $-40 \%$

Ashok Prajapati

Ashok Prajapati

Numerade Educator

Problem 53

A good lubricant should have
(a) high viscosity
(b) low viscosity
(c) moderate viscosity
(d) high density

Ashok Prajapati

Ashok Prajapati

Numerade Educator

Problem 54

A body of density $D_{1}$ and mass $M$ is moving downwards in glycerine of density $D_{2} .$ What is the viscous force acting on it?
(a) $M g\left(1-\frac{D_{2}}{D_{1}}\right)$
(b) $M g\left(1-\frac{D_{1}}{D_{2}}\right)$
(c) $M g D_{\text {1 }}$
(d) $M g D_{2}$

Mahendra K

Numerade Educator

Problem 55

The cylindrical tube of a spray pump has a cross-section of $8 \mathrm{~cm}^{2}$, one end of which has 40 fine holes each of area $10^{-8} \mathrm{~m}^{2}$. If the liquid flows inside the tube with a speed of $0.15 \mathrm{~m} / \mathrm{min}$, the speed with which the liquid is ejected through the holes is
(a) $50 \mathrm{~m} / \mathrm{s}$
(b) $5 \mathrm{~m} / \mathrm{s}$
(c) $0.05 \mathrm{~m} / \mathrm{s}$
(d) $0.5 \mathrm{~m} / \mathrm{s}$

Mahendra K

Numerade Educator

Problem 56

If the terminal speed of a sphere of gold (density $=19.5$ $\mathrm{kg} / \mathrm{m}^{3}$ ) is $0.2 \mathrm{~m} / \mathrm{s}$ in a viscous liquid $\left(\right.$ density $\left.=1.5 \mathrm{~kg} / \mathrm{m}^{3}\right)$
find the terminal speed of a sphere of silver (density = $10.5 \mathrm{~kg} / \mathrm{m}^{3}$ ) of the same size in the same liquid
(a) $0.2 \mathrm{~m} / \mathrm{s}$
(b) $0.4 \mathrm{~m} / \mathrm{s}$
(c) $0.133 \mathrm{~m} / \mathrm{s}$
(d) $0.1 \mathrm{~m} / \mathrm{s}$

Mahendra K

Numerade Educator

Problem 57

The working of venturimeter is based on
(a) Torricelli's law
(b) Pascal's law
(c) Bernoulli's theorem
(d) Archimedes principle

Ashok Prajapati

Ashok Prajapati

Numerade Educator

Problem 58

An application of Bernoulli's equation for fluid flow is found in
(a) Dynamic lift of an aeroplane
(b) Viscosity meter
(c) Capillary rise
(d) Hydraulic press

Ashok Prajapati

Ashok Prajapati

Numerade Educator

Problem 59

The working of an atomiser depends upon
(a) Bernoulli's theorem
(b) Boyle's law
(c) Archimedes principle
(d) Newton's law of motion

Ashok Prajapati

Ashok Prajapati

Numerade Educator

Problem 60

In stream line flow of liquid, the total energy of liquid is constant at
(a) all points
(b) inner points
(c) outer points
(d) None of these

Ashok Prajapati

Ashok Prajapati

Numerade Educator