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A layer of glycerine of thickness 1 mm is present between a large surface area and a surface area of 0.1 m2. With what force the small surface is to be pulled, so that it can move with a velocity of 1 ms-1? (Given that coefficient of viscosity = 0.07 kg m-1 s-1)

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Important Questions on Fluid Dynamics

EASY
If p is the density and η is coefficient of viscosity of fluid which flows with a speed v in the pipe of diameter d, the correct formula for Reynolds number Re is
EASY
Identify the incorrect statement regarding Reynold's number Re:
EASY
Oil is used for frying food materials rather than water, since oil
MEDIUM
Two capillary tubes of same length each of 50 cm but of different radii 4 mm and 2 mm are connected in series. When water flows, the pressure difference between the ends of the arrangement is P. Then the pressure difference between the ends of the first tube is
HARD
Water from a pipe is coming at a rate of 100 liters per minute. If the radius of the pipe is 5 cm, the Reynolds number for the flow is of the order of: (density of water = 100 kg/m3, coefficient of viscosity of water =1 mPa s)
HARD
Consider a thin square plate floating on a viscous liquid in a large tank. The height h of the liquid in the tank is much less than the width of the tank. The floating plate is pulled horizontally with a constant velocity u0. Which of the following statements is (are) true?
EASY

A flat plate of area 10 cm2 is separated form a large plate by a layer of Glycerine 1 mm thick. If the coefficient of viscosity of Glycerine is 20 poise, the force required to keep the plate moving with a velocity of 1 cm s-1 is       
 

HARD
Two tubes of radii r1 and r2 and lengths l1 and l2, respectively, are connected in series and a liquid flows through each of them in stream line conditions. P1 and P2 are pressure differences across the two tubes. If P2 is 4P1 and l2 is l 1 4 then the radius r2 will be equal to :
MEDIUM
A solid sphere of volume V experiences a viscous force F when descending with a speed v in a liquid. If another solid sphere of volume 27 V descends with the same speed v in the same liquid, it experiences a viscous force
HARD

A steel ball is dropped in a viscous liquid. The distance of the steel ball from the top of the liquid is shown below. The terminal velocity of the ball is closest to

 

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EASY
The relative viscosity of blood remains constant between
MEDIUM
If it takes 5 minutes to fill a 15 litre bucket from a water tap of diameter 2π cm then the Reynolds number for the flow is (density of water = 103  kg/m3 and viscosity of water=10-3 Pa.s ) close to:
EASY

A metal block of base area 0.20 m2 is placed on a table, as shown in figure. A liquid film of thickness 0.25 mm is inserted between the block and the table. The block is pushed by a horizontal force of 0.1 N and moves with a constant speed. If the viscosity of the liquid is 5.0×103 Pl, the speed of block is ______ ×10-3 m s-1.

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EASY
The velocity of upper layer of water in a river is 36 km h-1. Shearing stress between horizontal layers of water is 10-3 N m-2. Depth of the river is _____ m. (Co-efficient of viscosity of water is 10-2 Pa s)
EASY
A small sphere of radius r falls from rest in a viscous liquid. As a result, heat is produced due to viscous force. The rate of production of heat when the sphere attains terminal velocity, is proportional to
MEDIUM
A solid sphere, of radius R acquires a terminal velocity v1 when falling (due to gravity) through a viscous fluid having a coefficient of viscosity η. The sphere is broken into 27 identical solid spheres. If each of these spheres acquires a terminal velocity, v2, when falling through the same fluid, the ratio v1v2 equals:
MEDIUM
Which of the following option correctly describes the variation of the speed υ and acceleration 'a' of a point mass falling vertically in a viscous medium that applies a force F=-kυ , where 'k' is a constant, on the body? (Graphs are schematic and not drown to scale)
MEDIUM
The velocity of a small ball of mass M and density ρ, when dropped in a container filled with glycerine becomes constant after some time. If the density of glycerine is ρ2, then the viscous force acting on the ball will be:
EASY
The velocity of water in a river is 18 km h-1 near the surface. If the river is 5 m deep, find the shearing stress between the horizontal layers of water. The coefficient of viscosity of water=10-2 poise.
MEDIUM
The velocity of water in a river is 18 km h-1 near the surface. If the river is 5m deep, find the shearing stress between the horizontal layers of water. The coefficient of viscosity of water=10-2 poise.