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What is difference between rotational and irrotational flow?
 

Important Questions on Fluid Mechanics

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The cylindrical tube of a spray pump has radius R , one end of which has n fine holes, each of radius r . If the speed of the liquid in the tube is V , the speed of the ejection of the liquid through the holes is :
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What will be the nature of flow of water from a circular tap, when its flow rate increased from 0.18 L min-1 to 0.48 L min-1? The radius of the tap and viscosity of water are 0.5 cm and 10-3 Pa s, respectively. (Density of water : 103 kg m-3)

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The top of a water tank is open to air and its water level is maintained. It is giving out 0.74 m3 water per minute through a circular opening of 2 cm radius in its wall. The depth of the centre of the opening from the level of water in the tank is close to:
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Water containing air bubbles flows without turbulence through a horizontal pipe which has a region of narrow cross-section. In this region the bubbles
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A air bubble of radius 1 cm in water has an upward acceleration of 9.8 cm s2. The density of water is 1 gm cm3 and water offers negligible drag force on the bubble. The mass of the bubble is g = 980 cm/s2.
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The Bhagirathi and the Alaknanda merge at Deoprayag to form the Ganga with their speeds in the ratio 1: 1: 5 . The cross-sectional areas of the Bhagirathi, the Alaknanda and the Ganga are in the ratio 1: 2: 3 . Assuming streamline flow, the ratio of the speed of Ganga to that of the Alaknanda is
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Water flows into a large tank with flat bottom at the rate of 10-4 m3s-1. Water is also leaking out of a hole of area 1 cm2 at its bottom. If the height of the water in the tank remains steady then this height is:
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A small hole of area cross-section 2 mm2 is present near the bottom of a fully filled open tank of height 2 m. Taking g=10 m s-2, the rate of flow of water through the open hole would be nearly
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Air (density ρ ) is being blown on a soap film (surface tension T ) by a pipe of radius R with its opening right next to the film. The film is deformed and a bubble detaches from the film when the shape of the deformed surface is a hemisphere. Given that the dynamic pressure on the film due to the air blown at speed v is 12ρv2, the speed at which the bubble formed is
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A bubble of radius R in water of density ρ is expanding uniformly at speed v. Given that water is incompressible, the kinetic energy of water being pushed is
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Water is flowing at a speed of 1.5 m s-1 through a horizontal tube of cross-sectional area 10-2 m2 and you are trying to stop the flow by your palm. Assuming that the water stops immediately after hitting the palm, the minimum force that you must exert should be (density of water = 103 kg m-3)
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Physical processes are sometimes described visually by lines. Only the following can cross
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In the diagram shown, the difference in the two tubes of the manometer is 5 cm, the cross-section of the tube at A and B is 6 mm2 and 10 mm2 respectively. The rate at which water flows through the tube is g=10 m s-2

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A wind with speed 40 m s-1 blows parallel to the roof of a house. The area of the roof is 250 m2 . Assuming that the pressure inside the house is atmospheric pressure, the force exerted by the wind on the roof and the direction of the direction of the force will be : ρair =1.2 kg m-3 
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Consider a water jar of radius R that has water filled up to height H and is kept on a stand of height h (see figure). Through a hole of radius r r<<R at its bottom, the water leaks out and the stream of water coming down towards the ground has a shape like a funnel as shown in the figure. If the radius of the cross-section of water stream when it hits the ground is x. Then:
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Water flows in a horizontal tube (see figure). The pressure of water changes by 700 N m-2 between A and B where the area of cross section are 40 cm2 and 20 cm2, respectively. Find the rate of flow of water through the tube. (density of water =1000 kg m-3 )
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Water from a tap emerges vertically downwards with an initial speed of  1.0 ms-1 . The cross - sectional area of the tap is  10-4 m2 . Assume that the pressure is constant throughout the stream of water and that the flow is streamlined. The cross - sectional area of the stream, 0.15 m below the tap would be:
(Take  g=10 ms-2 )
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Consider the configuration of a stationary water tank of cross-section area A0 and a small bucket as shown in figure below;

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What should be the speed v of the bucket, so that the water leaking out of a hole of cross-section area A (as shown) from the water tank does not fall outside the bucket?

(Take, h=5 m, H=5 m, g=10 m s-2, A=5 cm2 and A0=500 cm2).

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A hollow spherical shell at outer radius R floats just submerged under the water surface. The inner radius of the shell is r . If the specific gravity of the shell material is 278 with respect to water, the value of r is:
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The approximate depth of an ocean is 2700 m . The compressibility of water is 45.4×10-11 Pa-1 and density of water is 103  kg/m 3. What fractional compression of water will be obtained at the bottom of the ocean ?