# Coefficient of Viscosity

## Trending Questions

**Q.**

What is meant by capillary depression?

**Q.**Which of the following correctly states how the viscosities of a liquid and a gas will change with temperature?

- Viscosity increases with the increase in temperature of a liquid and decreases with the increase in temperature of a gas.
- Viscosity increases with the increase in temperature of a liquid and increases with the increase in temperature of a gas.
- Viscosity decreases with the increase in temperature of a liquid and decreases with the increase in temperature of a gas.
- Viscosity decreases with the increase in temperature of a liquid and increases with the increase in temperature of a gas

**Q.**

How high a liquid will rise up a narrow tube as a result of capillary action depends on?

**Q.**The velocity distribution for the flow over a flat plate is given by u=2y−y2 in which u is the velocity in m/s at a distance y metres above the plate. Determine the shear stress at y=0.15 m. Take dynamic viscosity of the fluid as 8.5 poise.

- 1.455 N/m2
- 1.545 N/m2
- 1.445 N/m2
- 1.554 N/m2

**Q.**The velocity of water in a river is 18 km/hr at the surface. If the river is 5 m deep, find the shearing stress between the horizontal layers of water. The viscosity of water is 10−2 Poise.

- 10−3 N/m2
- 2×10−3 N/m2
- 3×10−3 N/m2
- 4×10−3 N/m2

**Q.**

Which of the following processes will be least affected by the viscosity of water ?

Water flowing through a pipe

Air bubble rising up through water

A wide, shallow sheet of water flowing on a flat surface

Water flowing out through a hole in the side of a tank

**Q.**Two horizontal plates placed 250 mm apart have an oil layer of viscosity 20 poise in between the plates. Calculate the shear stress on the oil layer, if the upper plate is moved with a velocity of 1250 mm/s.

- 20 N/m2
- 2 N/m2
- 10 N/m2
- None of the above mentioned.

**Q.**Which of the following graph shows the relation between shear stress and velocity gradient for a non-Newtonian fluid?

**Q.**The velocity of water in a river is 18 kmh−1 near the surface. If the river is 5 m deep, then the shearing stress between the surface layer and the bottom layer is:

(Given - coefficient of viscosity of water, η=10−3 Pa.s)

- 10−2 Nm−2
- 10−3 Nm−2
- 10−4 Nm−2
- 10−5 Nm−2

**Q.**There is a 1 mm thick layer of glycerine between a flat plate of area 100 cm2 & a big fixed plate. If the coefficient of viscosity of glycerine is 1.0 kg/m-s, then how much force is required to move the plate with a velocity of 7 cm/s?

- 7 N
- 0.7 N
- 0.007 N
- None of the above

**Q.**A Newtonian fluid fills the clearance between the shaft and the sleeve. When a force of 800 N is applied to the shaft, parallel to the sleeve, the shaft attains a speed of 1.5 cm/sec. If a force of 2.4 kN is applied instead, the shaft would move with a speed of

- 1.5 cm/sec
- 13.5 cm/sec
- 4.5 cm/sec
- None

**Q.**A square plate of 0.1 m side moves parallel to a second plate with a velocity of 0.1 m/s, both plates being immersed in water. If the viscous force is 0.002 N and the coefficient of viscosity is 0.01 poise, distance between the plates in m is

- 0.1
- 0.05
- 0.005
- 0.0005

**Q.**The space between two plates 20 cm×20 cm×1 cm, 1 cm apart is filled with a liquid of viscosity 1 Poise. The upper plate is dragged to the right with a force of F=5 N keeping the lower plate stationary. The upper plate is moving at a constant speed u as shown in figure.

What will be the velocity in m/s of the flow at a point 0.5 cm below the lower surface of the upper plate if linear velocity profile is assumed for the flow ?

- 1.25
- 2.5
- 6.25
- 0.25

**Q.**A square plate of 0.1 m side moves parallel to a second plate with a relative velocity of 0.1 m/s, both plates being immersed in water. If the viscous force is 0.002 N and the coefficient of viscosity is 0.01 Poise, distance between the plates in m is

- 0.1
- 0.05
- 0.005
- 0.0005

**Q.**

The space between two large horizontal metal plates 6cm apart is filled with a liquid of viscosity 0.8Ns/m2 . A thin planck of surface area 1m2is moved parallel to the length of the plates such that the planck is at a distance of 2cm from one plate and 4cm from the other.The force F required to drag it with a constant speed of is 1ms−1 is

20N

40N

60N

80N

**Q.**A boat of area 10 m2 floating on the surface of a river is made to move horizontally with a speed of 2 m/s by applying a tangential force. If the river is 1 m deep and the water in contact with the bed is stationary, find the tangential force needed to keep the boat moving with same velocity. (Assume the viscosity of water as 0.01 poise).

- 0.02 N
- 0.03 N
- 0.04 N
- 0.05 N

**Q.**A container filled with a viscous liquid is moving vertically downwards with a constant speed 3v0. At the instant shown, a sphere of radius r is moving vertically downwards (in liquid) has speed v0. There is no relative motion between fluid and container. The coefficient of viscosity is η. Then at the shown instant, the magnitude of viscous force acting on sphere is

- 6πηrv0
- 12πηrv0
- 18πηrv0
- 24πηrv0

**Q.**A plate of area 2 m2 is made to move horizontally with a speed of 2 m/s by applying a horizontal tangential force over the free surface of a liquid having depth of 1 m. If the coefficient of viscosity of liquid is 0.01 Poise, find the tangential force needed to move the plate.

- 4×10−3 N
- 3×10−3 N
- 2×10−3 N
- 1×10−3 N

**Q.**A rectangular metal plate has dimensions of 10 cm×20 cm. A thin film of oil separates the plate from a fixed horizontal surface. The separation between the lower surface of the rectangular plate and the upper portion of the horizontal surface is 0.2 mm. An ideal string is attached to the plate and passes over an ideal pulley to a mass m. When m=125 gm, the metal plate moves at a constant speed of 5 cm/s across the horizontal surface. Then, the coefficient of viscosity of oil in dyne-s/cm2 is (Use g=1000 cm/s2)

- 5
- 25
- 2.5
- 50

**Q.**A cubical block (side 2 m) of mass 20 kg slides on inclined plane lubricated with the oil of viscosity η=10−1 Poise with constant velocity of 10 m/s. Find out the thickness of the layer of liquid. (g=10m/s2)

- 4×10−3 m
- 3×10−3 m
- 2×10−3 m
- 1×10−3 m

**Q.**A cubical block of side ′a′ and denisty ′ρ′ slides over a fixed inclined plane with constant velocity ′v′. There is a thin film of viscous fluid of thickness ′t′ between the plane and the block. Then the coefficient of viscosity of thin film will be

- 3ρagt5v
- 4ρagt5v
- ρagtv
- None of these