EASY
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State properties of an ideal fluid. 

Important Questions on Fluid Dynamics

EASY
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.
MEDIUM
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 ?
MEDIUM
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:
HARD
Consider the wall of a dam to be straight with height H and length L. It holds a lake of water of height hh<H on one side. Let the density of water be ρw Denote the torque about the axis along the bottom length of the wall by τ1. Denote also a similar torque due to the water up to height h2 and wall length L2 by τ2. Then, τ1τ2 (ignore atmospheric pressure) is
MEDIUM
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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HARD
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
MEDIUM
A vessel completely filled with water has holes A and B at depths h and 3h from the top respectively. The hole A is a square of side L and B is a circle of radius r. The water flowing out per second from both the holes is same. Then L is equal to
HARD
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
MEDIUM
An ideal fluid flows (laminar flow) through a pipe of non-uniform diameter. The maximum and minimum diameters of the pipes are 6.4cm and 4.8cm , respectively. The ratio of the minimum and the maximum velocities of fluid in this pipe is:
EASY
A liquid is allowed to flow into a tube of truncated cone shape. Identify the correct statement from the following.
HARD

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).

MEDIUM
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)
MEDIUM

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)

EASY
Water flows through a horizontal pipe at a speed V. Internal diameter of the pipe is d. If the water is emerging at a speed V1 the diameter of the nozzle is
MEDIUM
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 )
EASY
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 :
HARD
An incompressible liquid of density ρ is enclosed with two frictionless pistons one of cross-sectional area A and the other of 4A. When the narrow piston moves in by a distance h, the wider piston moves out by a distance.
MEDIUM

Water stands at a depth of 15 m behind a reservoir dam. A horizontal pipe 4 cm in diameter passes through the dam 6 m below the surface 01 water as shown. There is a plug which secures the pipe opening. Then find the friction between the plug and pipe wall.

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EASY
Why is irrotational flow called potential flow?