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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
In a two dimensional steady flow the velocity of fluid particle at (x,y) is given by `vecV=(u_(0)+bx)hati-` by `hatj, u_(0)` and b are positive constants. Write the equation of streamilnes. Draw few streamlines for `xgt0`. |
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Answer» Correct Answer - `y=(c_(0))/(u_(0)+bx)` where `c_(0)` is a constant. For plot of stremlines see the solution. |
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| 2. |
To illustrate th principle of a rocket, a student designed a water rocket as shwon in the figure. It is basically a container having pressurized gas in its upper part and water in its lower part. Pressure of the gas is 4.0Mpa. Mass of empty container is 1.0kg and mass of its content is also 1.0kg. The nozzle at the bottom is opened to impart a vertical acceleration to the contaienr. If it is desired that the initial upwards acceleration of the container be 0.5g. what should be the cross sectional area (A) of the exit of the nozzle? Neglect the pressure due to height of water in the contaienr and take atmospheric pressure to be 1.0MPa. g=`10ms^(-2)`. |
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Answer» Correct Answer - `g=10ms^(-2)` |
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| 3. |
(i) A projected in still air. With respect to the ball the streamlines appear as shwon in the figure. At which point is the pressure larger -1 or 2? (ii) In the above figure if the ball is also spinning in clockwise sense, in which direction it will get deflected-up or down? |
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Answer» Correct Answer - (i) `P_(1)gtP_(2)` (ii) up |
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| 4. |
Explain some daily life examples based on capillarity. |
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Answer» Examples of Capillarity in Daily Life:
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| 5. |
Why do clouds float in the sky? |
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Answer» The final velocity of water drops is zero,so they appear to be floating in the sky. |
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| 6. |
A device used to measure the specific gravity of a liquid is called a hydrogmeter. In a simple hydrometer there is a cylindrical galss tube with some lead-weight at its bottom. The device floats in liquid while remaining vertical. The top part of the tube extends above the liquid and the divisions marked on the tube allows one to directly read the specific gravity of the liquid. The scale on the tube is calibrated such that in pure water it reads 1.0 at the water surface and a lenght `z_(0)` of the tube is submerged. calculate the specific gravity of the liquid if the liquid level is `DeltaZ` above the 1.0 mark. Disregard the curvature of the tube bottom. |
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Answer» Correct Answer - `(z_(0))/(z_(0)+Deltaz)` |
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| 7. |
State Pascal’s law. |
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Answer» Pascal’s law states that an increase in pressure at any point inside a liquid at rest is transmitted equally and without any change, in all directions to every other point in the liquid |
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| 8. |
Archimedes’ principle can also be applied to gases. |
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Answer» False Archimedes’ principle is about fluid displacement which does not involve gases. |
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| 9. |
A wooden stick of length `L`, radius `R` and density `rho` has a small metal piece of mass `m` ( of negligible volume) attached to its one end. Find the minimum value for the mass `m` (in terms of given parameters) that would make the stick float vertically in equilibrium in a liquid of density `sigma(gtrho)`. |
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Answer» Correct Answer - `piR^(3)Lrho(sqrt((sigma)/(rho))-1)` |
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| 10. |
A tiny liquid drop is spherical but a larger drop has oval shape? |
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Answer» Each free surface of a liquid behaves as a stretcjied membrane under the effect of surface tension and its nature is to bring the surface area to the minimum. Hence, the tiny drop is spherical but a large drop becomes oval under the effect of gravity. |
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| 11. |
In a machine, a fluid from a compressor, which is at high pressure, is allowed to pass through a nozzle. Cross section of the nozzle is shown in the fiuge. The nozzle consists of two sections of radii `r_(1)` and `r_(2)`. The nozzle is fixed on a stand with the help of a clamp. the clamp is a circular ring of radius `r_(1)` and width b. The fluid from the compressor is at a presssure of n times the atmospheric pressure `p_(0)`. assume that the entrie system is horizontal the fluid is ideal and the flow is steady. (a) what should be the volume flow rate so that pressure of the fluid at end B reduces to half of its value at end A? (b) If the entire system is kept in gravity free space and the net force on the nozzle due to the fluid flow is F then determine the minimum radial pressure that should be applied on the clamp. so the nozzle remains in place. Coefficient of friction betwwen clamp and nozzle is `mu`. (c) If a small hole is punched anywhere on the thinner part of the nozzle (close to end B) what should be the volume flow rate of the fluid so that it does not gush out? |
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Answer» Correct Answer - (a) `Q=pir_(1)^(2)r_(1)^(2)sqrt((nP_(0))/(rho(r_(1)^(4)-r_(2)^(4))))` (b) `(F)/(2pimur_(1)b)` (c) `Q=pi r_(1)^(2)r_(2)^(2)sqrt((2(n-1)P_(0))/(rho(r_(1)^(4)-r_(2)^(4))))` |
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| 12. |
A water tank has a small hole in its wall and a tapering nozzle has been fitted into the hole (figure). The diameter of the nozzle at the exit is `d_(0)=1cm`. The height of water in the tank above the central line of the nozzle is h=2.0m. Calculate the dischargerate in `m^(3)s^(-1)` through the nozzle. Another nozzle which is diverging outwards is fitted smoothly to the first nozzle. The pressure at the neck of the two nozzle (where diameter is `d_(0)`) drops ot 2.5m of water. Calculate the exit diameter (d) of the nozzle. Atmosphere pressure =10m of water and `g=10ms^(-2)` |
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Answer» Correct Answer - (a) `4.96xx10^(-4)m^(3)s^(-1)` (b) 1.48cm |
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| 13. |
A tightly fitted piston can slide along the inner wall of a long cylindrical pipe. With the piston at the lower end of the pipe, the lower end of the pipe is dipped into a large tank, filled with water. Now the piston is pulled up with the help of the rod attached to it. water rises in the pipe along with the piston. Why? To what maximum height water can be raised in the pipe using this method? What will be the answer to your question if water is replaced with mercuty? Atmosphere pressure is `P_("atm")=1.01xx10^(5)Pa`. |
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Answer» Correct Answer - 10.30m,0.76m |
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| 14. |
A cylindrical block of length 2l is made of two different materials. The uppwer half has density `d_(1)` and and lower half, which is heavier, has density `d_(2)` the block is floating in a liquid of unknown density d with `(l)/(2)` of its length outside the liquid. (a) Find d (b) Show that `dgt(4d_(1))/(3)` |
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Answer» Correct Answer - (a) `d=(2)/(3)(d_(1)+d_(2))` |
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| 15. |
A light cylinderical tube of length L=1.5m and radius `v=(1)/sqrt(pi)m` is open at one end. The tube containing air is inverted and pushed inside water as shown in figure. A block made of material of relative density 2 haas been placed on the flat upper surface of the tube and the whole system is in equilibrium Neglect the weight of air inside the tube and find the volume of block placed on the tube. |
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Answer» Correct Answer - `0.75 m^(3)` |
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| 16. |
A sealed balloon, filled with air, floats in water with `(1)/(3)` of its volume submerged. It was found that if it is pushed inside water at a depth h, it remains in equilibrium, neither sinking nor rising. Find h. Given that height of water barometer is 10m and temperature is constant at all depth. |
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Answer» Correct Answer - 20m |
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| 17. |
A bent tube contains water. An air bubble is trapped inside the liquid. The tube is held vertical (as shown) and is moved horizontally with an acceleration (a) such that the bubble moves to position `theta` shown in the diagram. Find the direction and magnitude of a. |
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Answer» Correct Answer - `a=g tan theta` towards right |
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| 18. |
A cyclindrical ice block is floating in water 10% of its total volume is outside water. Kerosene oil (relative density=0.8) is poured slowly on top of water in the container. Assume that the oil does not mix with water. Height of the ice cylinder is H. (a) As kerosene is poured, how does the volume of ice block above the water level change? (b) What is the thickness of kerosene layer above the water when 20% of the volume of the ice block is above the water surface? (c) Find the ratio of voume of ice block is kerosene to its volume in water after the kerosene layer rises above the top surface of ice and the block gets completely submerged. Neglect any melting of ice. |
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Answer» Correct Answer - (a) First increaes then become constant (b) `(H)/(2)` (c) 1.0 |
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| 19. |
A cylindrical wooden block of density half the density of water is floating in water in a cylindrical container. The cross section of the wooden block. And its height are A and h respectively. The cross sectional area of the container is 2A. The wooden block is pushed vertically so that it gradually gets immersed in water. Calculate the amount of work done in pushing the block. Density of water `=rho_(0)`. |
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Answer» Correct Answer - `W=(1)/(16)Arho_(0)gh^(2)` |
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| 20. |
A wooden block of cross sectional area A (in shape of a rectangle) has height h. It is held such that its lower surface touches the water surface in a wide and deep tank. The block is released in this positon. It oscillates for some time and then settles into its equilibrium positon. in equilibrium the block floats with its upper face just on the water surface. Calculate the amount of heat generated in the process assuming that the loss in gravitational potential energy of the system coprising of water and the block gets converted into heat. Density of water is `rho`. |
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Answer» Correct Answer - `(1)/(2)rhogAh^(2)` |
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| 21. |
A lake filled with water has depth H, A pipe of length slightly less than H lies at the bottom of the lake. It contains an ideal gas filled up to a length of `(H)/(10)` A smooth an ideal gas filled up to a length gas in place. Now the pipe is slowly raised to vertical position (see figure). Assume that temperature of the gas remains Constant and neglect the atmospheric pressure. (a) Plot the variation of pressure inside the lake as a function of height y from the base. Let the height of piston frm the base, after the pipe is made vertical, by y. plot the variation of gas pressure as a function of y in the first graph itself. (b) In equilibrium the gas pressure and the pressure due to water on the piston must be equal. Using this solve for equilibrium height `y_(0)` of the piston. You get two answers. Which one is correct and why? |
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Answer» Correct Answer - (b) `y=(H)/(2)-sqrt(15)/(10)H` |
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| 22. |
A cubical contaienr of side length L is filled completely with water. The container is closed. It is acclerated horizontally with acceleration a. Density of water is `rho`. (a) Assuming pressure at point 1 (upper right corner) to be zero, find pressure at point 2 (upper left corner). (b) Pressure at point 4, at a distance h vertically below point 2 , is same as pressure at lower right corner 3. find h. |
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Answer» Correct Answer - (a) `rhoaL` (b) `h=L(1-(a)/(g))` |
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| 23. |
Why is it difficult to fill mercury in a glass tube of mercury thermometer? |
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Answer» The inner radius of glass tube is very small and due to capillarity the mercury falls in the tube. Hence it is difficult to fill mercury in glass tube of the thermometer. |
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| 24. |
A hemispherical bowl of radius R is placed upside down on a flat horizontal surface. There is a small hole at the top of the inverted bowl. Through the hole, a liquid of density `rho` is poured in. Exactly when the container gets full, water starts leaking from between the table and the edge of the container. Find the mass (m) of the contaienr. |
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Answer» Correct Answer - `m=(piR^(3)rho)/(3)` |
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| 25. |
The device shown in fiugre can be used to measure the pressure and volume flow rate when a person exhales. There is a slit of width b running down th length of the cylinder. Inside the tube there is a light movable piston attached to an ideal spring of force constant K. In equiilibrium position the piston is at a position where the slit starts (shown by line AB in the figure. A person is made to exhale into the cylinder causing the piston to compress the spring. Assume that slit width b is very small and the outflow area is much smaller tan the cros section of the tube, even at the pistons full extension. A person exhales and the spring compresses by x. (Density of air=`rho`) (a) Calculate the gage pressure in the tube. (b) Calculate the volume flow rate (Q) of the air. |
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Answer» Correct Answer - (a) `(kx)/(piR^(2))` (b) `bx^(3//2)sqrt((2K)/(rhopiR^(2)))` |
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| 26. |
A vessel of volume `V_(0)` is completely filled with a salt solution having specific gravity `sigma_(0)`. Pure water is slowly added drop by drop to the container and the solution is allowed to overflow. (a) Find the specific gravity of the diluted solution in the contaienr when a volume V of pure water has been added to it. (b) If `sigma_(0)=1.2` then find the specific gravity of the solution in the container after a volume `V_(0)` of pure water has been added to it. (c) Plot the variation of `sigma` with V. |
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Answer» Correct Answer - (a) `sigma=1+(sigam_(0)-1)e^(-v//v_(0))` (b) 1.074 |
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| 27. |
Why it is easy to swim in river water than in sea water? |
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Answer» Due to the presence of dissolved salts in sea water is denser than river water which makes floating easier and hence swimming is easier. |
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| 28. |
Hydraulic press is used in the extraction of oil from oil seeds. |
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Answer» Hydraulic press is used in the extraction of oil from oil seeds is True. |
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| 29. |
What is meant by atmospheric pressure? |
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Answer» The pressure exerted by the atmospheric gases on its surroundings and on the surface of the earth is called atmospheric pressure. |
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| 30. |
With an appropriate illustration prove that the force acting on a smaller area exerts a greater pressure. |
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Answer» Consider standing on loose sand. Your feet go deep into the sand. Now, when you lie down on the sand, you will find that your body will not go that deep into the sand. In both the cases the force exerted on the sand is the weight of your body which is the same. This force acting perpendicular to the surface is called thrust. When you stand on loose sand, the force is acting on an area equal to the area of your feet. When you lie down, the same force acts on an area of your whole body, which is larger than the area of your feet. Therefore the effect of thrust, that is, pressure depends on the area on which it acts. The effect of thrust on sand is larger while ‘ standing than lying. |
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| 31. |
What is critical velocity? |
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Answer» Critical velocity is the limiting velocity above which the fluid flow is turbulent and below which the fluid flow is streamlined. |
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| 32. |
Density of mercury is 13600 kg m-3 . Calculate the relative density. |
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Answer» Relative Ddensity = \(\frac{Density\, of\, Mercury}{Density \,of\, water}\) at 4°C R.D. = 13.6 |
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| 33. |
The density of water is 1 g cm-3 . What is its density in S.I. units? |
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Answer» S.I. unit of density of water = \(\frac { 1000kg }{ m^3}\) |
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| 34. |
A block of wood of weight 200 g floats on the surface of water. If the volume of block is 300 cm3 calculate the upthrust due to water. |
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Answer» Upthrust of floating object = weight of the water displaced Weight = mg = 0.200Kg × \((\frac { 10m }{ s^2})\) = 2N |
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| 35. |
A rectangular container has been filled with an ideal gluid and placed on an incline plane. The inclination of the incline is `theta`. Find the angle that the liquid surface will make with the incline surface as the contaienr slides down. Find your answer for following two cases. |
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Answer» Correct Answer - (a) 0 (b) `tan^(-1)mu` |
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| 36. |
A cylindrical vessel of radius R=1m and height H=3m is filled with an ideal liquid up to a height of h=2 m. the contaienr with liquid is rotated about its central vertical axis such that the liquid just rises to the brim. Calculate the angular speed `(omega)` of the container. |
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Answer» Correct Answer - `omega=2sqrt(10)"rads"^(-1)` |
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| 37. |
A water clock consist of a vessel which has a small orifice O. The upper contaienr is filled with water which trickless down into the lower contaienr. The shape of the (upper or lower) contaienr is such that height of water in the upeer container changes at a uniform rate. What should be the shape of the container? Assume that atmospheric air can enter inside the lower container through a hole in it taht the upper container is open at the top. Vessel is axially symmetric. |
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Answer» Correct Answer - The vessel can be obtained by revolution of a curve `z=kx^(4)` |
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| 38. |
The weight of fluid displaced determines the buoyant force on an object. |
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Answer» The weight of fluid displaced determines the buoyant force on an object isTrue . |
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| 39. |
Match the following.Column - IColumn - II(a) Density(i) hpg(b)1 gwt(ii) Milk(c) Pascal’s law(iii) \(\frac{Mass}{Volume}\)(d) Pressure exerted by a fluid(iv) Pressure(e) Lactometer(v) 980 dyne |
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Answer» (a) (iii) (b) (v) (c) (iv) (d) (i) (e) (ii) |
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| 40. |
What is meant by Reynold’s number? |
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Answer» It is a pure number that tells about the nature of fluid flow inside the pipe. |
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| 41. |
A horizontal tube having cross sectional area `A_(1)=10cm^(2)` has a venturi connected to it having cross sectional area `A_(2)=4 cm^(2)`. A moanometer, having mercury as its liquid is connected to be has uniform cross section and it has a horizontal part of lenght L=10cm. When there is no flow in the tube the height of mercuty column in both vertical arms is H=12cm. calculate the minimum flow rate (in `m^(3)//s`) of air through the tube if it is required that the entire amount of mercury move to one vertical arm of the manometer. Gives, density of `Hg=13.6xx10^(3)kgm^(3)`, density of air=1.2 kg `m^(-3)`. |
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Answer» Correct Answer - `12.1m^(3)s^(-1)` |
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| 42. |
What is the effect of temperature on the viscosity of the liquid? |
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Answer» Viscosity decreases on increasing the temperature. |
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| 43. |
At which temperature, the surface tension of liquid is zero? |
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Answer» At critical temperature, the surface tension of liquid is zero. |
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| 44. |
A manometer has a vertical arm of cross sectional area 9A and an inclined arm having area of cross section A. The density of the manometer liquid has a specific gravity of 0.74. the scale attached to the inclined arm can read up to `+-0.5mm`. It is desired that the manometer shall record pressure difference `(P_(1)-P_(2))` up to an accuracy of `+- 0.09` mm of water. To acheive this, what should be the inclination angle `theta` of the inclined arm. |
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Answer» Correct Answer - `theta=sin^(-1)(0.13)` |
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| 45. |
Two identical containers have the same volume of water in it. Each of them is placed on a balnce and redings of the two balances are same. There is a hollow ball and a solid ball that have same volume. The hollow ball floats in water and the solid ball sinks. A string from the ceiling suspends the solid ball so that it remains completely submerged in the water in the first container. The hollow ball is held submerged in the water in the second container and is held by a stringfastened to the bottom of the container. which balance will show higher reading? How will your answer change if the string in the second container is car? |
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Answer» Correct Answer - First balance will shw higher reading. Answer will not change if string in 2nd container is cut. |
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| 46. |
In a pressure cooker, the food is cooked faster because ……..(a) increased pressure lowers the boiling point (b) increased pressure raises the boiling point (c) decreased pressure raises the boiling point (d) increased pressure lowers the melting point |
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Answer» (a) increased pressure lowers the boiling point |
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| 47. |
A large container has a sliding vertical wall of height H so as to divide it into two parts. The partition wall is connected to the left container wall by an ideal spring of force constant k. when the spring is relaxed the dimentsions of the floor of the right part is Lxxb. Now water (density `rho`) is slowly poured into the right chamber. what is the maximum volume of water that can be stored in the right chamber without spilling it into the other part. The partition wall slides without friction. |
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Answer» Correct Answer - `Hb(L+(rhogbH^(2))/(2K))` |
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| 48. |
The figure shows a non-viscous, incompressible and steady flow in front of a sphere. A-B is a horizontal streamline. It is known that the fluid velocity along this streamline is given by `V=V_(0)(1+(R^(3))/(x^(3))).V_(0)` is velocity of flow on this streamline when `xrarr(-oo)`. It is given that pressure at `xrarr(-oo)` is `P_(0)` and density of liquid is `rho`. (i) Write the variation of pressure along the streamline from pointA, far away from the sphere, to point B on the spehre. (ii) Plot the variation of pressure along the streamline from `x=-oo` to x=-R. |
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Answer» Correct Answer - (i) `P=P_(0)+rhoV_(0)^(2)[1-(1_(R^(3))/(x^(3)))]` |
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| 49. |
An open rectangular tank 5mxx4mxx3m in dimension is containing water up to a height of 2m the tank is accelerated horizontally along the longer side. Assuming water to be and ideal liquid find- (a) the maximum acceleration with which the tank can be moved so that water does not fall from the rear side. (b) the gauge pressure at the bottom of the front and back of the tank (points A and B) if the tank is closed at the top and is then acclerated horizontally at `9 m//s^(2)`. Assume that the top cover has a small hole at the right side of the tank so taht pressure of air inside the tank is maintained at atmospheric pressure. Gauge pressure at a point is difference in absolute pressure at the point and atmospheric pressure. |
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Answer» Correct Answer - (a) `(2g)/(5)=4m//s^(2)` (b) `P_(A)=0,P_(B)=0.44` atm |
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| 50. |
A cylindrical tank having radius R is half filled with water having density `rho`. There is a hole at the top of the tank. The tank is moved horizontally. Perpendiular to its length, with a constant acceleration equal to the acceleration due to gravity (g). Find the maximum pressure exerted by water at any point on the tank. Atmospheric pressure is `P_(0)`. Assume that there is no spillage. |
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Answer» Correct Answer - `P_(0)+sqrt(2)rhogR` |
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