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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.
| 551. |
We can cut an apple easity with a sharp knife as compared to a blunt knife? Explain why? |
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Answer» Correct Answer - Sharp kinife applies more pressure as compare to blunt knife because of lesser area of contact. Sharp knife applies more pressure as compare to blunt knife because of lesser area of contact. |
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| 552. |
If two identical mercury drops are combined to form a single drop, then its temperature willA. decreaseB. increasesC. remains the sameD. None of these |
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Answer» Correct Answer - B Surface energy of combined drop will be lowered, so excess surface energy will raise the temperature of the drop |
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| 553. |
A water proofing agent chages the angle of contact fromA. from acute to `90^(@)`B. from obtuse to `90^(@)`C. from an acute to obtuse valueD. from an obtuse to acute value |
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Answer» Correct Answer - C Water proofing agents increases angle of contact. |
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| 554. |
Uniform speed of 2 cm diameter ball is `20cm//s` in a viscous liquid. Then, the speed of 1 cm diameter ball in the same liquid isA. `5cms^(-1)`B. `10cms^(-1)`C. `40cms^(-1)`D. `80cms^(-1)` |
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Answer» Correct Answer - A `v_(T)prop r^(2)` ltbr) Radius or diameter is half. So, uniform or terminal speed is `(1)/(4)`th. |
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| 555. |
A Newtonian fluid fills the clearance between a shaft and a sleeve. When a force of `800N` is applied to the shaft, parallel to the sleeve, the shaft attains a speed of `1.5cm//sec`. If a force of `2.4kN` is applied instead, the shaft would move with a speed ofA. `1.5cm//sec`B. `13.5cm//sec`C. `4.5cm//sec`D. None |
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Answer» Correct Answer - C `Fpropv` `(F_(2))/(F_(1))=(v_(2))/(v_(1))impliesv_(2)=((2400)/(800))xx1.5impliesv_(2)=4.5cm//s` |
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| 556. |
What is the absolute pressure on a swimmer `10 m` below the surface of a lake? Take atmospheric pressure `1xx10^(5)N//m^(2)` |
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Answer» Pressure at any depth `h` from the free surface of the water is given by `P=rhogh+P_(a)` `=(1000)xx10xx10+1.0xx10^(5)=2.00N//m^(2)` |
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| 557. |
Choose the correct options.A. Viscosity of liquids increases with temperatureB. Viscosity of gases increases with temperatureC. surface tension of liquids decreases with temperatureD. For angle of contact`(theta)=(0^@)`, liquid neither rises nor falls on capillary |
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Answer» Correct Answer - B::C For contact angle `theta=90^(@)`, liquid neither rises nor falls. |
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| 558. |
A plank is floating in a non-viscous liquid as shown, Choose the correct option A. Equilibrium of plank is stable in vertical directionB. For small oscillations of plank in vertical direction motion is simple harmonicC. Even if oscillations are large, motion is simple harmonic till it is not fully immersedD. On vertical displacement motion is periodic but not simple harmonic |
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Answer» Correct Answer - A::B::C Restroing force `=-(rho Ag)x` or `F prop -x` This is just like a spring - block system of force constant `K=rho Ag`. |
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| 559. |
A cubical block of wood of edge 3 cm floats in water. The lower surface of the cube just touches the free end of a vertical spring fixed at the bottom of the pot. Find the maximum weight that can be put on the block without wetting it. Density of wood `=800kg//m^(3)` and spring constant of the spring `=50N//m`. Take `g=10m//s^(2)`A. 0.1 NB. 0.35 NC. 0.5 ND. 0.7 N |
| Answer» Correct Answer - D | |
| 560. |
A cubical block of wood of edge 3 cm floats in water. The lower surface of the cube just touches the free end of a vertical spring fixed at the bottom of the pot. Find the maximum weight that can be put on the block without wetting it. Density of wood =`800 kgm^-3` and spring constant of the spring `=50Nm^-1 Take g=10ms^-2`. , |
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Answer» Correct Answer - C::D Fraction of volume immersed before putting the new weigh `=(rho_(block))/(rho_(water))=(800)/(1000)=0.8` i.e. `20%` of` 3 cm` or `0.6 cm` is above water. Let w is the new weight, then spring will be compressed by `0.6 cm` `:. w+`weight of block=Upthrust on whole volume of block `+` spring force or, `w=(3xx10^(-2))^(3)xx1000xx10+50xx` `(0.6xx10^(-2))=(3xx10^(-2))^(3)xx800xx10` `:. w=0.354 N`. |
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| 561. |
A block of wood has a mass of `25g`. When a `5g` metal piece with a volume of `2cm^(3)` is attached to the bottom of the block, the wood barely floats in water. What is the volume `V` of the wood? |
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Answer» Correct Answer - B::C Weight=upthrust `:. (25+5)g=(V+2)rho_(w)g` Putting `rho_(w)=1g//cm^(3)` we get, `V=28 cm^(3)`. |
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| 562. |
A liquid flows through a horizontal tube. The velocities of the liquid in the two sections, which have areas of cross section `A_(1)` and `A_(2)` are `v_(1)` and `v_(2)` respectively. The difference in the levels of the liquid in the two vertical tubes is `h`. Then A. the volume of the liquid flowing through the tube in unit time is `A_(1)v_(1)`B. `v_(2)-v_(1)=sqrt(2gh)`C. `v_(2)^(2)-v_(1)^(2)=2gh`D. the energy per unit mass of the liquid is the same in both sections of the tube |
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Answer» Correct Answer - A::C::D `(P_(1))/(rho)+(v_(1)^(2))/2=(P_(2))/(rho)+(v_(2)^(2))/2` `P_(1)-P_(2)=(rho)/2(v_(2)^(2)-v_(1)^(2))` But `P_(1)-P_(2)=rhogh=(rho)/2(v_(2)^(2)-v_(1)^(2))` or `v_(2)^(2)-v_(1)^(2)=2gh` |
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| 563. |
The figure shown a pipe of uniform cross-section inclined in a vertical plane. A U-tube manometer is connected between the point A and B. If the liquid of density `rho_(0)` flows with velocity `v_(0)` in the pipe. Then the reading h of the manometer is A. `h=0`B. `h=(v_(0)^(2))/(2g)`C. `h=(rho_0)/(rho)((v_(0)^(2))/(2g))`D. `h=(rho_(0) H)/(rho-rho_(0))` |
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Answer» Correct Answer - A From continuity equation, `v_(A)=v_(B)=v_(0)` `:. p_(A)=rhogh=p_(B)+0` `:. p_(B)-p_(A)=rhogh` …(i) Now, let us make pressure equation from manometer. `p_(A)+rho g (h+H)=rho_(Hg) gh=p_(3)` Putting `p_(B)-p_(A)=rhogh we get h=0`. |
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| 564. |
A container is partially filled with a liquid of density `rho_2` A capillary tube of radius r is vertically inserted in this liquid. Now another liquid of density `rho_1(rho_1ltrho_2)` is slowly poured in the container to a height h as shown. There is only denser liquid in the capillary tube. The rise of denser liquid in the capillary tube is also `h`. Assuming zero contact angle, the surface tension of heavier liquid isA. `r rho_(2) gh`B. `2pirrho_(2) gh`C. `r/2 (rho_(2)-rho_(1))gh`D. `2pir(rho_(2)-rho_(1)) gh` |
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Answer» Correct Answer - C `P_(0)+rho_(1)g h-rho_(2) g h +(2T)/r=P_(0)` `rArr T=r/2 (rho_(2)-rho_(1)) gh` |
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| 565. |
The height of mercury barometer is h when the atmospheic pressure is `10^(5)Pa`. The pressure at x in the shown diagram is A. `10^(5)Pa`B. `0.8xx10^(5)Pa`C. `0.2xx10^(5)Pa`D. `120xx10^(5)Pa` |
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Answer» Correct Answer - B `h rho g=10^(5)Pa` (given) `:. p_(x)=(h+(h)/(5)) rho g=0.8 h rhog` `=0.8xx10^(5)Pa`. |
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| 566. |
The height of a mercury barometer is 75 cm at sea level and 50 cm at the top of a hill. Ratio of density of mercury to that of air is 10. The height of the hill isA. `250 m`B. `2.5 km`C. `1.25 km`D. `750 km` |
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Answer» Correct Answer - B |
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| 567. |
The height of a mercury barometer is 75 cm at sea level and 50 cm at the top of a hill. Ration of density of mercury to that of air is `10^(4)`. The height of the hill isA. `250 m`B. `2.5 km`C. `1.25 km`D. `750 m` |
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Answer» Correct Answer - B Difference of pressure between sea level and the top of hill `DeltaP =(h_(1)-h_(2))xxrho_(Hg)xxg=(75-50)xx10^(-2)xxrho_(Hg)xxg" "……(i)` and pressure difference due to h meter of air `DeltaP =hxxrho_("air")xxg" "….(ii)` By equating (i) and (ii) we get `hxx rho_("air")xx g =(75-50) xx 10^(-2) xx rho_(Hg) xx g` `therefore h=25xx10^(-2)((rho_(Hg))/(rho_(air))) = 25xx10^(-2)xx10^(4) = 2500 m therefore " Height of the hill" = 2.5 km`. |
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| 568. |
A ball is made of a material of density `rho` where `rho_(oil)ltrholtrho_(water)` with `rho_(oil)` and `rho_(water)` representing the densities of oil and water, respectively. The oil and water are immiscible. If the above ball is in equilibrium in a mixture of this oil and water, which of the following pictures represents its equilibrium position?A. B. C. D. |
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Answer» Correct Answer - B For equilibrium, weight should be balanced by buoyant force. density of oil lt density of water and ball should be in between oil and water. |
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| 569. |
A small ball of density `rho` is immersed in a liquid of density `sigma(gtrho)` to a depth `h` and released. The height above the surface of water up to which the ball will jump isA. `(sigma/rho-1)h`B. `(rho/sigma-1)h`C. `(rho/sigma+1)h`D. `(sigma/rho+1)h` |
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Answer» Correct Answer - A Let `V` be the volume of the ball. Net upward acceleration. `a=(Vsigmag-Vrhog)/(Vrho)=((sigma-rho)gh)/rho` If `h_(a)` is the height in air to which the ball rises, then `0-(2(sigma-rho)gh)/rho=2(-g)h_(a)` `:. H_(a)=((sigma-r)gh)/(grho)=(sigma/rho-1)h` |
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| 570. |
A water hose pipe of cross-sectional area `5cm^(2)` is used to fill a tank of `120L`. It has been observed that it takes 2 min to fill the tank. Now, a nozzel with an opening of cross-sectional area `1cm^(2)` is attached to the hose. The nozzel is held so that water is projected horizontally from a point 1m above the ground. The horizontal distance over which the water can be projected is (Take `g=10m//s^(2))`.A. `3m`B. `8m`C. `4.47m`D. `8.64 m` |
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Answer» Correct Answer - C Volume flow rate `=av=(V)/(t)` `:. v_(1)=(V)/(A_(1) t)=(120xx10^(-3))/(5xx10^(-4)xx2xx60)` Now, `A_(1)v_(1)=A_(2)v_(2)` `A_(2)` is `(1)/(5)`th of `A_(1)`. Hence, `v_(2)` is five times of `v_(1)` or `10m//s` `t_(0)=sqrt((2h)/(g))=sqrt((2xx1)/(10))` `=0.447s` `R=v_(2)t_(0)=4.47m`. |
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| 571. |
A lawn sprinkler has `20` holes, each of cross-sectional area `2.0 x 10^(-2) cm^(2)`, and is connected to a hose pipe of cross sectional area `2.4 cm^(2)`. If the speed of water in the hose pipe is `1.5 ms^(-1)`, the speed of water as it emerges from the holes isA. `2.25ms^(-1)`B. `4.5ms^(-1)`C. `9ms^(-1)`D. `18ms^(-1)` |
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Answer» Correct Answer - C `(2.4xx10^(-4))xx1.5=20x2xx10^(-2)xx10^(-4)xxv` or `v=(2.4xx1.5xx10^(2))/40 ms^(-1) =(24xx15)/40ms^(-1)=9ms^(-1)` |
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| 572. |
A cylinder of height 20m is completely filled with water. The velocity of effux of water `(in ms^(-1))` through a small hole on the side wall of the cylinder near its bottom isA. `10`B. `20`C. `25.5`D. `5` |
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Answer» Correct Answer - B `v=sqrt(2gh) = sqrt(2xx10xx20)=20m//s` |
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| 573. |
When a large bubble rises from the bottom of a lake to the surface its radius doubles. If atmospheric pressure is equal to that of column of water height H then the depth of lake isA. `H`B. `2H`C. `7H`D. `8H` |
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Answer» Correct Answer - C |
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| 574. |
Two soap bubbles of radii `r_(1)` and `r_(2)` equal to 4 cm and 5 cm are touching each other over a common surface `S_(1)S_(2)` (shown in figure). Its radius will be A. `4cm`B. `20cm`C. `5cm`D. `4.5cm` |
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Answer» Correct Answer - B Radius of curvature of common surface of double bubble `r=(r_(2)r_(1))/(r_(2)-r_(1)) = (5xx4)/(5-4) = 20cm` |
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| 575. |
Prove that if two bubbles of radii `r_(1)` and `r_(2)(r_(1)ltr_(2))` come in contact with each other then the radius of curvature of the common surface `r=(r_(1)r_(2))/(r_(2)-r_(1))` |
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Answer» Correct Answer - `r=(r_(1)r_(2))/(r_(1)-r_(2))` `(4S)/(r )= (4S)/(r_(2))-(4S)/(r_(1))` `(1)/(r )= (1)/(r_(2))-(1)/(r_(1))` `r=(r_(1)-r_(2))/(r_(1)r_(2))` |
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| 576. |
Prove that if two bubbles of radii `r_(1)` and `r_(2)(r_(1)ltr_(2))` come in contact with each other then the radius of curvature of the common surface `r=(r_(1)r_(2))/(r_(2)-r_(1))`A. `r_(2)-r_(1)`B. `(r_(2)-r_(1))/(r_(1)r_(2))`C. `(r_(1)r_(2))/(r_(2)-r_(1))`D. `r_(2)+r_(1)` |
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Answer» Correct Answer - C Radius of curvature of common surface is, `R_("Common")=(r_(1)r_(2))/(r_(2)-r_(1))` |
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| 577. |
There is a 1mm thick layer of glycerine between a flat plate of area `100cm^(2)` and and a big plate. If te coefficient of viscosity of glycerine is `1.0kg//m-sec`, then how much force is required to move the plate with a velocity of 7 cm/sec.A. `3.5N`B. `0.7N`C. `1.4N`D. None |
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Answer» Correct Answer - B `F=etaA(dv)/(dx)" "impliesF=(1xx10^(-2)xx7xx10^(-2))/(10^(-3))impliesF=0.7N` |
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| 578. |
A 10 cm long wire is placed horizontal on the surface of water and is gently pulled up with a force of `2xx10^(-2)` N to keep the wire in equilibrium. The surface tension, in `Nm^(-1)` of water isA. 0.1B. 0.2C. 0.001D. 0.002 |
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Answer» Correct Answer - A Surface tension`T=(F)/(2l)=(2xx10^(-2))/(2xx10xx10^(-2))=0.1 Nm^(-1)`,. |
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| 579. |
An iron casting has a number of cavities in it. It weighs `6000 N` in air and `4000 N` in water. Determine the total volume of all the cavities in the casting. The density of iron (without cavities) is `8.0 g//cm^(3), rho_(w)= I g//cm^(3)`. |
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Answer» Volume of the cavities `V_("cav")` can be determined by taking difference between the volume `V_("cast")` of the casting as a whole and the volume of the iron in the casting `V_("cav")=V_("cast")-V_("iron")` `V_("iron")=W/(rho_(iron)g)` `W` is the weight of casting `W_("eff")=W-rho_(w)gV_("cast")` `V_("cast")=(W-W_("eff"))/(rho_(w)g)impliesV_("cav")=(W-W_("eff"))/(rho_(w)g)-W/(8rho_("iron"))` `(6000-4000)/((10^(3))(10))-6000/((10)(8xx10^(3)))=0.125m^(3)` |
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| 580. |
The wattability of a surface by a liquid depends primarily onA. viscosityB. surface tension of liquid and airC. densityD. angle of contact between the surface and the liquid |
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Answer» Correct Answer - D The value of an angle of contact determines whether a liquid will spread on the surface. |
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| 581. |
Two holes are made in the side of the tank such that the jets of water flowing out of them meet at the same point on the ground. If one hole is at a height of `3 cm` above the bottom, then the distance of the other holes from the top surface of water isA. `3/2 cm`B. `sqrt(6)cm`C. `sqrt(3)cm`D. `3 cm` |
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Answer» Correct Answer - D `x= sqrt(2 gh_(1)) xx sqrt((2h_(2))/(g)) or x = 2 sqrt(h_(1)h_(2))` Now, imagine a hole at a depth `h_(2)` below the free surface of the liquid. The height of this hole will be `h_(1)`. Clearly, `x` remains the same. |
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| 582. |
A water tank of height `H`, completely filled with water is placed on a level ground. It has two holes one at a depth `h` from top and the other at height `h` form its base. The water ejecting from both holesA. both the holes will fall at the same spotB. upper hole will fall farther than that form the lower holeC. upper hole will fall closer than that form the lower holeD. more information is required. |
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Answer» Correct Answer - A Velocity of water coming out from hole `A` v_(1) = sqrt(2gh)` Velocity of water coming out from hole B `=v_(2)=sqrt(2g(H-h))` Time taken by water to reach the ground from hole `A` `=t_(1) = sqrt(2(H-h)//g)` Time taken by water to reach the ground from hole `B` `=t_(2) = sqrt(2h//g)` Obviously, range on the ground for both is the same `:. R = v_(1)t_(1) = v_(2)t_(2) = 2gsqrt(h(H-h))`. |
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| 583. |
figure shows two holes in a wide tank containing a liquid common. The water streams coming out of these holes strike the ground at the same point. The heigth of liquid column in the tank is A. `10cm`B. `8cm`C. `9.8 cm`D. `980 cm` |
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Answer» Correct Answer - A `4(H-4) = 6(H-6)` or `2 H = 36-16-20 or H=10 cm`. |
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| 584. |
Water from a tap emerges vertically downwards with an initial spped of `1.0ms^-1`. The cross-sectional area of the tap is `10^-4m^2`. Assume that the pressure is constant throughout the stream of water, and that the flow is steady. The cross-sectional area of the stream 0.15 m below the tap isA. `5.0xx10^(-4) m^(2)`B. `1.0xx10^(-5)m^(2)`C. `5.0xx10^(-5) m^(2)`D. `2.0xx10^(-5) m^(2)` |
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Answer» Correct Answer - C Decrease in potential energy = increase in kinetic energy `therefore" "rhogh=1/2rho(v_(f)^(2)-v_(i)^(2))` `or" "2(10)(0.15)-v_(f)^(2)-(10)^(2)` `or" "v_(f)= 2 ms^(-1)` Now, from continuity equation, `A_(1)v_(1)=A_(2)v_(2)" or "Aprop1/v` Velocity has become two times, Hence, area of cross-section will remain half. |
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| 585. |
Assertion: Liquids and gases are largely incompressible and densities are therefore, nearly constant at all pressure. Reason: Liquids exhibit a large variation in densities with pressure by gases do not.A. If both assertion and reason are true and reason is the correct explanation of assertionB. If both assertion and reason are true but reason is not the correct explanation of assertionC. if assertion is true but reason is false.D. if both assertion and reason are false. |
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Answer» Correct Answer - D A liquid is largely incompressible and its density is constant at all pressure. Gases exhibit a large variation indensities with pressure. |
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| 586. |
Assertion: The velocity increases, when water flowing in broader pipe enter a narrow pipe. Reason: According to equation of continuity, product of area and velocity is constant.A. Statement I is true, statement II is true and Statement II is a correct explanation for Statement I.B. Statement I is true, Statement II is true and Statement II is NOT the correct explanation for Statement I.C. Statement I is true, Statement II is false.D. Statement I is false, Statement II is true. |
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Answer» Correct Answer - A Continuity equation `av=const.` If area of pipe is less velocity of water will be more. |
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| 587. |
Assertion: The velocity increases, when water flowing in broader pipe enter a narrow pipe. Reason: According to equation of continuity, product of area and velocity is constant.A. If both assertion and reason are true and reason is the correct explanation of assertionB. If both assertion and reason are true but reason is not the correct explanation of assertionC. if assertion is true but reason is false.D. if both assertion and reason are false. |
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Answer» Correct Answer - A In a streamlines flow of a liquid, according to equation of continuity `av`=constant. Where `a` is the area of cross section and `v` is the velocity of liquid flow. When water flowing in a broader pipe enters a narrow pipe, the area of cross section of water decreases therefore the velocity of water increases. |
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| 588. |
Assertion : The velocity of fall of a man jumping with a parachute first increases and then becomes constant. Reason : The constant velocity of fall of man is called terminal velocity.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true and the reason is not the correct explanation of the assertion.C. If assertion ture but reason is false.D. If the assertion and reason both are false. |
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Answer» Correct Answer - B |
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