InterviewSolution
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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.
| 51. |
A contaienr havng an ideal liquid of density `rho` is moving with a constant acceleration of `hata=a_(x)hati+a_(z)hatk` where x direction is horizontal and z is vertically upwards. The container is open at the top. In a reference frame attached to the contaienr with origin at bottom corner (see figure), write the pressure at a point inside the liquid at co-ordinates (x,y,z). The pressure is `P_(0)` at origin. |
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Answer» Correct Answer - `P=P_(0)-rhoa_(x),x-rho(g+a_(z))_(z)` |
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| 52. |
(i) A non uniform cube of side length a is kept inside a container as shown in the figure. The average density of the material of the cube is 2 `rho` where `rho` is the density of water. Water is gradually fille din the container. It is observed that the cube begins to topple, about its edge into the plane of the figure passing through pointA, when the height of the water in the container becomes `(a)/(2)`. Find the distance of the centre of mass of the cube from the face AB of the cube. Assume that water seeps under the cube. (ii) A rectangular concrete block (specific gravity =2.5) is used as a retatining wall in a reservoir of water. The height and width of the block are x and y respectively the height of water in the reservoir is `z=(3)/(4)x`. the concrete block cannot slide on the horizontal base but can rotate about an axis perpendicular to the plane of the figure and passing through point A (a) Calculate the minimum value of the ratio `(y)/(x)` for which the block will not begin to overturn about A. (b) Redo the above problem for the case when there is a seepage and a thin film of water is present under the block. Assume that a seal at A prevents the water from flowing out underneath the block. |
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Answer» Correct Answer - (i) `x=(9)/(8)` (ii) (a) `(3)/(4sqrt(10))` (b) `(3)/(4sqrt(7))` |
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| 53. |
A centrifuge has a horizontal cylinder rotating about a vetical axis as shown in the figure. Water inside it has density `rho`. (a) Consider a point A. Inside the liquid, at a distance r from the rotation axis. Liquid pressurea t his point is P. Write the value of `(dP)/(dr)` when the cylinder, with all its liquid. rotates uniformly at an angular speed `omega`. (ii) Consider a small disc shaped foreign material inside the centrifuge at point A. The area of circular disc is `DeltaS` and its thickness is `Deltar`. It disc is in position so that its circular face is vertical. Find the radial acceleration of the disc with respect to the cylinder when angular speed of rotation is |
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Answer» Correct Answer - (a) `(dP)/(dr)=rhoomega^(2)r` (b) `(1-(rho)/(rho))omega^(2)r` |
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| 54. |
At what temperature, the surface tension of water is maximum? |
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Answer» Surface tension of water is maximum at 4 °C because the density of water is maximum at 4°C. |
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| 55. |
What is the advantage of ploughing the field? |
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Answer» By ploughing the soil, the small capillaries in the soil break down, hence the water does not evaporate through them. This keeps the field moisturised for a long time which helps in germination of seeds. |
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| 56. |
What is the effect on angle of contact on mixing soap solution in water? |
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Answer» The angle of contact decreases. |
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| 57. |
What is an ideal liquid? |
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Answer» A liquid which is non-compressible and non-viscous is called ideal liquid. In real no liquid is ideal as viscosity and compressibility is not zero for any liquid. |
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| 58. |
What is the angle of contact for pure water and glass? |
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Answer» The angle of contact for pure water and glass is zero. |
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| 59. |
There is high pressure on the bottom of sea, then how animals survive? |
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Answer» There is high pressure at the bottom of the sea. To balance out this pressure, the fishes and other sea animals have extra air dissolved in their blood. This internal fluid pressure balances the high pressure and animals are able to survive. This is the reason why fishes die when they are brought out of water because outside water the internal fluid pressure exceeds the external atmospheric pressure and their veins burst. |
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| 60. |
Define streamline flow. |
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Answer» Streamline flow (also called flow) is a type of flow of fluid in which fluid travels in regular paths. In streamline flow, the velocity, pressure and other such properties remain constant in fluid at each point. |
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| 61. |
Name the force responsible for surface tension. |
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Answer» Cohesive force. |
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| 62. |
Define turbulent flow. |
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Answer» Turbulent flow is a type of flow of fluid in which the fluid travels in irregular path. In this type of flow, the speed of the fluid at a point undergoes changes continuously in both magnitude and direction. Most kinds of fluid flow are turbulent. Example : flow of air and water. |
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| 63. |
How many types of energies are there in a flowing liquid? |
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Answer» A flowing liquid has three types of energies :
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| 64. |
A horizontal glass tube is filled with mercury. The tube thas three different cross sections as shwn: with `A_(1)=18cm^(2),A_(2)=8cm^(2)` and `A_(3)=9cm^(2)`. The piston is pushed so as to throw out mercury at a constant speed of v=6m/s at the other end of the tube. Assume that mercuty is an ideal fluid with density `rho_(Hg)=1.36xx10^(4)kg//m^(3)`. Take `g=10m//s^(2)P_("atm")=1.01xx10^(5)Pa` (i) Find the force needed to push the piston assuming that friction force between the piston and the tube wal is f=40N (ii) Find the height (h) of mercury column in the attached vertical tube. What happens to this height if the piston is pushed with smaller speed? |
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Answer» Correct Answer - (i)371.2N (ii) 26cm. Height h will increase |
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| 65. |
A liquid is flowing in a horizontal pipe of uniform cross section at a speed v. Two tubes A an B are inserted into the pipe as shown. Assume the flow to remain streamiline inside the pipe. (a) The diagram depicts that height of liquid in tube B`(=h_(2))` is more than the height of liquid in tube `A(=h_(1))` is it correct? (b) Calculate the difference in height of the liquid in two tubes. |
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Answer» Correct Answer - Yes (b) `h_(2)-h_(1)=(v_(2))/(2g)` |
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| 66. |
A bent tube is lowered into a water stream as shown in figure. The velocity of the stream is `V_(1)`. The closed upper end is located at a height `h_(0) ` and has a small orifice. To what height `h` will the liquid get spurt? |
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Answer» Correct Answer - `(v^(2))/(2g)-h_(0)` |
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| 67. |
How does an object’s density determine whether the object will sink or float in water? |
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Answer» Whether an object will sink or float in a liquid is determined by the density of the object compared to the density of the liquid. If the density of a substance is less than the density of the liquid it will float. For example, a piece of wood which is less dense than water will float on it. Any substance having more density than water (for example, a stone), will sink into water. |
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| 68. |
On what factors the pressure exerted by the liquid depends on? |
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Answer» Pressure exerted by a liquid at a point is determined by
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| 69. |
Fill in tha blanks. 1. The weight of the body immersed in a liquid appears to be ………than its actual weight 2. The instrument used to measure atmospheric pressure is ……….3. The magnitude of buoyant force acting on an object immersed in a liquid depends on ………of the liquid. 4. A drinking straw works on the existence of ………… |
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Answer» 1. less 2. barometer 3. density 4. Pressure |
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| 70. |
A cylinder of length L floats with its entire length immersed in two liquids as shown in the fig. The upper liquid is water and the lower liquid has density twice that of water. The two liquid are immiscible. The cylinder is in equilibrium with its `(3)/(4)` lenght in the denser liquid and `(1)/(4)` of its length in water. The thickness of water layer is `(L)/(4)` only. Find. (a) the specific gravity of the material of the cylinder. (b) the time period of oscillations if the cylinder is depressed by some small distance `(lt(L)/(4))` and released. Neglect viscosity and change in level of liquids when the cylinder moves. |
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Answer» Correct Answer - (a) `(7)/(4)` (b) `pisqrt((7L)/(4g))[1+(1)/sqrt(2)]` |
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| 71. |
(i) A toy boat made of steel is floating in a beaker having water. The beaker is placed on a spring balance. The boat tilts and sinks into water. (a) Will the level of water in the beaker go up or fall down? (b) Will the reding of spring balance decrease or increase? (iii) You are in a boat on a calm lake. There is a floating log near you . You pick the log and put it into the boat. What happesn to the level of water in the lake? Does it rise or fall? |
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Answer» Correct Answer - (i) (a) Fall down (b) Not change (iii) Does not change. |
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