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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.
| 251. |
An aeroplane of mass 5000 kg is flying at an altitude of 3 km. if the area of the wings is `50m^(2)` and pressure at the lower surface of wings is `0.6xx10^(5)Pa`, the pressure on the upper surface of wings is (in pascal) `(g=10ms^(-2))`A. `59xx10^(3)`B. `2xx10^(4)`C. `6xx10^(3)`D. `59` |
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Answer» Correct Answer - A `(p_(1)-p_(2))A=mg` |
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| 252. |
Cylindrical block of area of cross-section A and of material of density `rho` is placed in a liquid of density one third of density of block. The block compress in the spring is one-third of te length of the block. if acceleration due to gravity is g, the spring constant of the spring isA. `rhoAg`B. `2rhoAg`C. `2rhoAg//3`D. `rho Ag//3` |
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Answer» Correct Answer - B `mg=F_(b)+kx rArr Al rhog =(Alrhog)/(3) + k((l)/(3))` `rArr k = 2 A rho g` |
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| 253. |
Water is flowing through a horizontal tube. The pressure of the liquid in the portion where velocity is `2m//s` is 2 m of Hg. What will be the pressure in the portion where velocity is `4m//s`A. `2.66xx10^(5)Pa`B. `2.78xx10^(5)Pa`C. `2.84xx10^(5)Pa`D. `2.60xx10^(5)Pa` |
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Answer» Correct Answer - A `P+rhogh+(1)/(2)rhov^(2)=`constant |
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| 254. |
If l is length of the tube and r is the radius of the tube, then the rate of volume flow of a liquid is maximum for the following measurements. Under the same pressure difference.A. `l,r`B. `(l)/(2),2r`C. `l,(r)/(2)`D. `2l,2r` |
| Answer» Correct Answer - B | |
| 255. |
Which factor better controls the flow rate of a liquid throught the syringe?A. the pressure exerted by the thumbB. the length of the needleC. the nature of the liquidD. the radius of the syringe bore. |
| Answer» Correct Answer - D | |
| 256. |
Surface tension of water is `T_(1)`. When oil spreads on water surface tension becomes `T_(2)`, thenA. `T_(1)gtT_(2)`B. `T_(1)=T_(2)`C. `T_(1)ltT_(2)`D. `T_(1)=(T_(2))/(2)` |
| Answer» Correct Answer - A | |
| 257. |
As the depth of the river increases, the velocity of flowA. increasesB. decreasesC. remains unchangedD. may increase or decrease |
| Answer» Correct Answer - B | |
| 258. |
The addition of soap changes the surface tension of water to `T_(1)` and that of salt solution changes to `T_(2)`. ThenA. `T_(1)=T_(2)`B. `T_(1)gtT_(2)`C. `T_(1)ltT_(2)`D. `T_(1)geT_(2)` |
| Answer» Correct Answer - C | |
| 259. |
Adding detergents to the water increases itsA. Surface tensionB. Angle of contactC. Wetting actionD. Viscosity |
| Answer» Correct Answer - C | |
| 260. |
The surface tension of a liquid at its boiling point isA. maximumB. zeroC. same as at room temperatureD. minimum but more than zero |
| Answer» Correct Answer - B | |
| 261. |
Mercury does not wet glass, wood or iron becauseA. cohesive force is less than adhesive forceB. cohesive force is greater than adhesive forceC. angle of contact is less than `90^(0)`D. cohesive force is equal to adhesive force |
| Answer» Correct Answer - B | |
| 262. |
A liquid does not wet a solid surface if the angle of contact for the given pair of liquid and solid surfaces isA. `0^(@)`B. `90^(@)`C. `60^(@)`D. `120^(@)` |
| Answer» Correct Answer - D | |
| 263. |
A liquid will not wet the surface of a solid if the angle of contact isA. zeroB. equal to`45^(@)`C. equal to`90^(@)`D. greater than `90^(@)` |
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Answer» Correct Answer - D A liquid does not wet the solid surfaces if the angle of contact is obtuse (i.e., `theta gt 90^(@)`). |
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| 264. |
A vessel contains (density `d`) over mercury (density `D`). A homogenous solid sphere floats with half of its volume in mercury and the other half in the oil . The density of the material of the sphere isA. `sqrt(Dd)`B. `(2Dd)/(D+d)`C. `(D+d)/(2)`D. `(Dd)/(D+d)` |
| Answer» `Vd_(b)g=V_(1)dg+V_(2)Dg` | |
| 265. |
A volume V of a viscous liquid flows per unit time due to a pressure head `DeltaP` along a pipe of diameter d and length l. instead of this pipe a set of four pipes each of diameter `(d)/(2)` and length 2l is connected to the same pressure head `DeltaP`. Now the volume of liquid flowing per unit time is:A. VB. `(V)/(4)`C. `(V)/(8)`D. `(V)/(16)` |
| Answer» `(1)/(R_(P))=(1)/(R_(1))+(1)/(R_(2))+(1)/(R_(3))+(1)/(R_(4))impliesR_(P)=(R)/(4),Q=(pipr^(4))/(8etal)` | |
| 266. |
The lower end of a capillary tube of diameter 2.0 mm is dipped 8.00cm below the surface of water in a beaker. What is the pressure required in the tube in order to blow a hemispherical bubble at its end in water? The surface tension of water at temperature of the experiments is `7.30 xx 10^(-2) Nm^(-1)`. 1 atmospheric pressure =` 1.01 xx 10^(5) Pa`, density of water `= 1000 kg//m^(3), g=9.80 ms^(-2)`. also calculate the excess pressure. |
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Answer» The excess pressure in a bubble of gas in a liquid is given by 2S/r, where S is the surface tension of the liquid-gas interface. You should note there is only one liquid surface in this case. (for a bubble of liquid in a gas, there are two liquid surface, so the formula for excess pressure in that case is 4S/r.) the radius of the bubble is r. Now the pressure outside the bubble `P_(o)` equals atmospheric pressure plus the pressure due to 8.00 cm of water column. that is `P_(o)=(1.01xx10^(5)Pa+0.08mxx1000kgm^(-3)xx9.80ms^(-2))` `=1.01784xx10^(5)Pa` Therefore,t he pressure inside the bubble is `P_(i)=P_(o)+2S//r` `=1.01784xx10^(5)Pa+(2xx7.3xx10^(-2)Pa" "m//10^(-3)m)` `=(1.01784+0.00146)xx10^(5)Pa` `=1.02xx10^(5)Pa` Where the radius of the bubble is taken to be equal to the radius of the capillary tube, since the bubble is hemispherical! (The answer has been rounded off the three significant figures). the excess pressure in the bubble is 146 Pa. |
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| 267. |
Two balls of same size but different masses `m_(1)` and `m_(2)(m_(2)gtm_(1))` are attached to the two ends of a thin light thread and dropped from a certain height. It is known that the ciscous drag of air depends on the size and velocities of the balls. other than the gravitational pull from the earth and the viscous drag, the buoyant force from air also act on the balls, the buoyant force on a ball equals to the wweight of air displaced by the ball. After sufficiently long time from the instant the balls were dropped both of them acquire uniform velocity known as terminal velocity. When the balls have acquired terminal velocity, the tension in the thread isA. zeroB. `(m_(2)-m_(1))g`C. `0.5(m_(2)+m_(1))g`D. `0.5(m_(2)-m_(1))g` |
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Answer» Correct Answer - D For vertical translational equilibrium use freebody diagram for single and two body system separately. |
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| 268. |
A bucket of water contain a wooden block floating in water with `(4//5)`th of its volume sub merged in the water. The bucket is placed on the floor of a lift and the lift now starts moving down with uniform acceleration. The block of wood nowA. moves upwardB. moves downwardC. remains at same placeD. moves horizontally |
| Answer» Correct Answer - C | |
| 269. |
A wooden block is floating in a water tank. The block is pressed to its bottom. During this process, work done is equal to :A. work done against upthrust exerted by the waterB. Work done against upthrust plus loss of gravitational potential energy of the blockC. Work done against upthrust minus loss of ravitational potential energy of the blockD. all the above |
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Answer» Correct Answer - C Initially the wooden block floats with partially immersed in water. Initiall upthrust exerted by water is equal to weight of the block. But when it is pressed down more water is displaced. Hence upthrust exerted by water increases. The force requried to press down the block is equal to `F="upthrust"-mg` Hence, work done by the force F will be equal to work done against (upthrust -mg). It means, work done by external force is equal to work done against upthrust loss of gravitational potential energy of the block. |
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| 270. |
Mercury of density `rho_(m)` is poured into cylinderical communicating vessels of cross-sectional area 2A and A respectively. A solid iron cube of volume `V_(0)` and relative density 2 is dropped into the broad vessel, and as a result the level of the mercury in it rises. Then, water is poured into the broader vessel until the mercury reaches the previous level in it. Find the height of water column if it does not submerge the block. |
| Answer» `(2v_(0))/(A+v_(0).^(2//3))` process. | |
| 271. |
The fig shows a semo-cylinderical massless gate of unit length perpendicular to the plane of the page and is pivoted at the point `O` holding a stationary liquid of density `rho`. A horizontal foce `F` is applied at its lowest position to keep it stationary. The magnitude of the force is:A. `(3)/(2)rhogR^(2)`B. `(9)/(2)rhogR^(2)`C. `rhogR^(2)`D. `2rhogR^(2)` |
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Answer» Correct Answer - D Torque about `O` due to water pressure is given by `tau=int d tau` When `dtau=dF.Rsintheta` after intergrating from 0 to `180^(@)` we will get `tau=4R^(3)rhog` this should be balanced by applied torque. `becausetau=4R^(3)rhog=F(2R)` `impliesF=2rhogR^(2)` |
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| 272. |
The diameter of an air-bubble formed at the bottom of a pond is `d=4mum`, when the bubble rises to the surface, its diameter increases `n=1.1` times. If expansion of air bubble is assumed to be isothermal and atmospheric pressure to be standard. How deep the pond at the spot is [surface tension of water `0.075(N)/(m)`]A. 2.5 mB. 10 mC. 7.5 mD. 5 m |
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Answer» Correct Answer - D `hrhog=P_(0)(n^(3)-1)+(4T(n^(2)-1))/(d)` |
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| 273. |
(a) What is the largest average velocity of blood flow in an artery of radius `2xx10^(-3)m` if the flow must remian laminar? (b) What is the corresponding flow rate? Take viscosity of blood to be `2.084xx10^(-3)Pa-s`. Density of blood is `1.06xx10^(3)kg//m^(3)`. |
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Answer» here `r=2xx10^(-3)m,D=2r=2xx2xx10^(-3)=4xx10^(-3)m,` `eta=2.084xx10^(-3)" "Pa-s," "rho=1.06xx10^(3)kgm^(-3)` For flow to be laminar, `N_(R)=2000` (a). Now, `v_(C)=(N_(R)eta)/(rhoD)=(2000xx(2.084xx10^(-3)))/((1.06xx10^(3))xx(4xx10^(-3)))=0.98m//s`. (b). volume flowing per second `=pir^(2)v_(c)=(22)/(7)xx(2xx10^(-3))^(2)xx0.98=1.23xx10^(-5)m^(3)s^(-1)` |
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| 274. |
The flow of blood in a large artery of a anesthetized dog is diverted through a venturimeter. The wider part of the meter has a cross-sectional area equal to that of the artery. Ie., `10mm^(2)` . The narrower part has an area `5 mm^(2)`. The pressure drop in the artery is `22 Pa`. Density of the blood pressure drop in the artery is `22Pa`. Density of the blood pressure drop in the artery is `22Pa`. Density of the blood is `1.06xx10^(3)kgm^(-3)`. The speed of the blood in the artery isA. `0.12 m s^(-1)`B. `0.62 m s^(-1)`C. `0.24 m s^(-1)`D. `0.42 m s^(-1)` |
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Answer» Correct Answer - A Here, A=10 `"mm"^(2), a=5 "mm"^(2),` `rho=1.06xx10^(3)kg m^(-3)=1060 kg m^(-3), P_(1)-P_(2)=22 Pa` Speed of the fluid through the wide neck is `v=sqrt((2(P_(1)-P_(2)))/(rho)){((A)/(a))^(2)-1}^(-1//2)` or `(A)/(a)=(10)/(5)=2` `therefore v=sqrt((2xx22)/(1060(2^(2)-1)))=0.12 m s^(-1)` |
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| 275. |
Ice berg floats in water with part of it submerged. What is the fraction of the volume of iceberg suberged, if the density of ice is `rho_(l)=0.917g//cm^(3)`?A. 0.917B. `(1000)/(917)`C. `(83)/(1000)`D. `(1000)/(83)` |
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Answer» Correct Answer - A `mg=rho_("ice")v_("ice")g=rho_(w)v_("inside")g` |
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| 276. |
A hydraulic press with the larger piston of diameter 35 cm at a heigth of 1.5 m relative to the smaller piston of diameter 10 cm. The mass on the smaller piston is 20 kg. What is the force exerted on the load placed. On the larger piston ? The density of oil in the press is `750 kg m^(-3)`A. `5xx10^(3)N`B. `1.3xx10^(3)N`C. `3.7xx10^(3)N`D. `4.8xx10^(3)N` |
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Answer» Correct Answer - B `(F_(1))/(A_(1))=(F_(2))/(A_(2))=hrhog,(m_(1)g)/(pir_(1)^(2))-(m_(2)g)/(pir_(2)^(2))=hrhog` |
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| 277. |
Two pistons of a hydraulic machine have diameters of 30.0 cm and 2.5 cm. What is the force exerted on the larger pistion when 40 kg wt. is placed on the smaller piston? If the smaller pistion moves in through 6 cm, how much does the other pistion move out ? |
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Answer» For smaller piston, Area `a_(1) = pi xx (1.25)^(2) cm^(2)` For larger piston, Area `a_(2) = pi xx (15)^(2) cm^(2)` Mechanical advantage at the larger piston is `(a_(2))/(a_(1))` `therefore F_(2) = (a_(2))/(a_(1)) xx F_(1) = (pi(15)^(2))/(pi(1.25)^(2))xx 40` kg wt `=(225)/(1.25 xx 1.25) xx 40 xx 9.8 N` = 56,448 N This is the force exerted on the larger piston. The liquids are considered incompressible. Therefore volume covered by the movement of smaller piston inwards is equal to that moved outwards by larger piston. `rArr l_(1) a_(1) = l_(2) a_(2)` `rArr l_(2) =(a_(1))/(a_(2))l_(1) = ((1.25)^(2))/((15)^(2))xx 6 cm` = 0.042 cm So, the distance moved out by the larger piston is 0.042 cm. |
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| 278. |
The Reynolds number of a flow is the ratio ofA. Viscous force and gravitational forceB. Inertial force and viscous forceC. Inertial force and gravitational forceD. Viscous force and surface energy |
| Answer» Correct Answer - B | |
| 279. |
The radius of one arm of a hydraulic lift is three times the radius of the other arm. What force should be applied on the narrow arm so as to lift 50 kg at the wider arm?A. 60 NB. 54.4 NC. 26.7 ND. 30 N |
| Answer» Correct Answer - B | |
| 280. |
What are the dimensions of Reynolds number ? |
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Answer» `R = (rhov_(0)D)/(eta)` `(rho` is density of the fluid `v_(0)` is the critical velocity, D is diameter through which the fluid is flowing and `eta` is the coefficient of viscosity of the fluid) `R([ML^(-3)][LT^(-1)][L])/([ML^(-1)T^(-1)])=[(ML^(-1)T^(-1))/(ML^(-1)T^(-1))]=[M^(0)L^(0)T^(0)]` `:. R` is dimensionless. |
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| 281. |
Pressure has the dimensionsA. `[ML^(-1)T^(-2)]`B. `[ML^(-0)T^(-1)]`C. `[ML^(1)T^(-1)]`D. `[ML T^(-2)]` |
| Answer» Correct Answer - A | |
| 282. |
In the following figure, four beakers of different base areas contain water as shown The pressure at the bottom is maximum for the beakerA. AB. BC. CD. Same for all |
| Answer» Correct Answer - D | |
| 283. |
For an ideal fluid viscosity isA. zeroB. infinityC. finite but smallD. unity |
| Answer» Correct Answer - A | |
| 284. |
When stirring of a liquid is stopped, the liquid comes to rest due toA. surface tensionB. gravityC. viscosityD. buoyancy |
| Answer» Correct Answer - C | |
| 285. |
A good lubricant must haveA. high viscosityB. low viscosityC. high densityD. low surface tension |
| Answer» Correct Answer - A | |
| 286. |
Viscosity is exhibited byA. solids liquids and gasesB. liquids andd gasesC. solids and gasesD. solids and liquids |
| Answer» Correct Answer - B | |
| 287. |
Viscosity of water at constant temperature isA. more in deep waterB. more in shallow watersC. less in deep waterD. same in both dep water and shallow waters |
| Answer» Correct Answer - A | |
| 288. |
Is viscosity a vector ? |
| Answer» Viscosity is a property of liquid it does not have any direction, hence it is a scaler quantity. | |
| 289. |
In the following fig., the flow of liquid through a horizontal pipe is shown. Three tubes A, B and C are connected to the pipe. The radii of the tubes `A,B and C` at the junction are respectively `2 cm, 1 cm and 2 cm`. It can be said that the A. in A is maximumB. in A and C is equalC. is same in all the threeD. in A and B is same |
| Answer» Correct Answer - C | |
| 290. |
A wooden block, with a coin placed on its top, floats in water as shown in figure. The distance l and h are shown here. After some time the coin falls into water. Then A. l decreases and h increasesB. l increases and h decreasesC. both l and h increaseD. both l and h decrease |
| Answer» Correct Answer - D | |
| 291. |
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. `(aL)/(2g)`B. `(gL)/(2a)`C. `(gL)/(a)`D. `(aL)/(g)` |
| Answer» Correct Answer - D | |
| 292. |
A wooden cube floats just inside the water, when a mass of x(in grams) is placed on it. If the mass is removed, the cube floats with a height `(x)/(100)` (cm) above the water surface. The length of the side of cube is (density of water is 1000 `kg//m^(3)`)A. 10 cmB. 15 cmC. 20 cmD. 30 cm |
| Answer» Correct Answer - A | |
| 293. |
The surface tension and vapour pressure of water at `20^(@)C` is `7.28xx10^(-2)Nm^(-1)` and `2.33xx10^(3)Pa`, respectively. What is the radius of the smallest spherical water droplet which can form without evaporating at `20^(@)C`? |
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Answer» Given, surface tension of water `" "(S)=7.28xx10^(-2) N//m` Vapour pressure (p) `=2.33xx10^(3)` Pa The drop will evaporate, if the water pressure is greater than the vapour pressure. Let a water droplet or radius R can be formed without evaporating. Vapour pressure=Excess pressure in drop. `therefore p=(2S)/(R)` or `R=(2S)/(p)=(2xx7.28xx10^(-2))/(2.33xx10^(3))` `=6.25xx10^(-5)` m |
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| 294. |
The surface tension and vapour pressure of water at `20^(@)C` is `7.28xx10^(-2)Nm^(-1)` and `2.33xx10^(3)Pa`, respectively. What is the radius of the smalalest spherical water droplet which can form without evaporating at `20^(@)C`?A. `3.125xx10^(-5)m`B. `12.5xx10^(-5)m`C. `6.25xx10^(-5)m`D. none of these |
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Answer» Correct Answer - C The excess pressure `(2T//r)` should be greater than the vapour pressure. Then the drop will evaporate Vapour pressure `=` Excess pressure in drop. |
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| 295. |
A wooden cube is found to float in water with `½cm` of its vertical side above the water. On keeping a weight of 50 gm over its top, it is just submerged in the water. The specific gravity of wood isA. 0.8B. 0.9C. 0.85D. 0.95 |
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Answer» Correct Answer - D Weight of the body `=` weight of displaced liquid `rho_(b)V_(b)+50=V_(b)rho_("water")` |
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| 296. |
The opening near the bottom of the vessel shown in the figure has an area `A`. A disc is held against the opening keep the liquid from running out. Let `F_(1)` be the net forces on the disc applied by liquid and air in this case. Now the disc is moved away from the opening a short distance. The liquid comes out and strikes the disc in elastically. Let `F_(2)` be the force exerted by the liquid in this condition. The `F_(1)//F_(2)` is |
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Answer» Correct Answer - 2 `F_(1)=DeltaP(A)=rhoghA` `F_(2)=rhoAV^(2)=rhoA(2gh),(F_(2))/(F_(1))=2` |
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| 297. |
A cylindrical tank of height 2 m is open at the top and has a radius 50 cm. Water is filled in it upto a height 1.75 m. Calculate how long it will take to empty the tank through a hole of radius 0.05 cm in its bottom. |
| Answer» `10^(6) sqrt(0.35) s` | |
| 298. |
A solid body is found floating in water with `((alpha)/(beta))^(th)` of its volume submerged. The same solid is found floating in a liquid with `((alpha)/(beta))^(th)`of its volume above the liquid surface. The specific gravity of the liquid isA. `(beta-alpha)/(alpha)`B. `(alpha-beta)/(beta)`C. `(alpha)/(beta-alpha)`D. `(beta)/(alpha-beta)` |
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Answer» Correct Answer - C `(alpha)/(beta)=(d_(b))/(d_(w))` ….(1) `1-(alpha)/(beta)=(d_(b))/(d_(1))` …(2) From 1 and 2 `(d_(l))/(d_(b))=(alpha)/(beta-alpha)` |
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| 299. |
Water is flowing through a capillary tube at the rate of `20xx10^(-6)m^(3)//s`. Another tube of same radius and double the length is connected in series to the first tube. Now the rate of flow of water in `m^(3)s^(-1)` isA. `20xx10^(-6)`B. `40xx10^(-6)`C. `0`D. `10xx10^(-6)` |
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Answer» Correct Answer - 4 `Q=alpha(1)/(l),(Q_(1))/(Q_(2))=(2l)/(l)` |
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| 300. |
Tanks A and B open at the top contain who different liquids upto certain height in them. A hole is made on the wall of each tank at a depth `h` from the surface of the liquid. The area of the hole in `A` is twice that of in `B`. If the liquid mass flux through each hole is equal, then the ratio of the densities of the liquids respectively isA. `(2)/(1)`B. `(3)/(2)`C. `(2)/(3)`D. `(1)/(2)` |
| Answer» `(m)/(t)="constant",rho_(1)A_(1)V=rho_(2)A_(2)Vimpliesrho_(1)A_(1)=rho_(2)A_(2)` | |