The following questions relate to viscosity. a. What are the primary dimensions of

A system is separated from its surrounding by a a. border b. boundary c. dashed line d. dividing surface

How are density and specific weight related?

Density is (select all that apply) a. weight/volume b. mass/volume c. volume/mass d. mass/weight

Which of these arc units of density? (select all that apply) a. kglm3 b. mglcm3 c. lbm/ft3 d. slug/ft3

Specific gravity (select all that apply) a. can have units of N/m3 b. is dimensionless c. increases with temperature d. decreases with temperature

If a liquid has a specific gravity of 1.7, what is the density in .JSS per cubic feet? What is the specific weight in lbf per cubic feet?

What are SG, -y, and p for mercury? State your answers in SI ..ruts and in traditional units.

If a gas has -y = 15 N/m3 , what is its density? State your .mswers in SI units and in traditional units.

If you have a bulk modulus of elasticity that is a very ...rge number, then a small change in pressure would cause a. a very large change in volume b. a very small change in volume

The bulk modulus of elasticity of ethyl alcohol is a6 X I 09 Pa. for water, it is 2. 15 X I 09 Pa. Which of 'lese liquids is easier to compress?

A pressure of2 X 106 N/m2 is applied to a mass of water that initially filled a 2000 cm3 volume. Estimate its volume after the pressure is applied.

Calculate the pressure increase that must be applied to water to reduce its volume by 2%.

An open vat in a food processing plant contains 400 L of water at 20C and atmospheric pressure. If the water is heated to 80C, what will be the percentage change in its volume? If the vat has a diameter of 3 m, how much will the water level rise due to this temperature increase?

Where in this text can you find: a. density data for such liquids as oil and mercury? b. specific weight data for air (at standard atmospheric pressure) at different temperatures? c. specific gravity data for sea water and kerosene?

Regarding water and seawater: a. Which is more dense, seawater or freshwater? b. Find (SI units) the density of seawater (1 0C, 3.3% salinity). c. Find the same in traditional units. d . What pressure is specified for the values in (b) and (c)?

If the density, p, of air (in an open system at atmospheric' pressure) increases by a factor of 1.4x due to a temperature change, a. specific weight increases by I .4x b. specific weight increases by 13.7x c. specific weight remains the same

The following questions relate to viscosity. a. What are the primary dimensions of viscosity? What are five common units? b. What is the viscosity of SAE lOW-30 motor oil at II 5F (in traditional units)?

Shear stress has dimensions of a. force/area b. dimensionless

For the velocity gradient dV/ dy a. the change in velocity dV is in the direction of flow b. the change in velocity dV is perpendicular to flow

The no-slip condition a. only applies to ideal flow b. only applies to rough surfaces c. means velocity, V, is zero at the wall d. means velocity, V, is the velocity of the wall

Kinematic viscosity (select all that apply) a. is another name for absolute viscosity b. is viscosity/density c. is dimensionless because forces are canceled out d. has dimensions of L2 /T e. is only used with compressible fluids

What is the change in the viscosity and density of water between l0C and 70C? What is the change in the viscosity and density of air between l0C and 70C? Assume standard atmospheric pressure (p =- I 0 I kN/m2 absolute).

Determine the change in the kinematic viscosity of air that is heated from 10C to 70C. Assume standard atmospheric pressure.

Find the dynamic and kinematic viscosities of kerosene, SAE I OW-30 motor oil, and water at a temperature of 38C (l00F).

What is the ratio of the dynamic viscosity of air to that of water at standard pressure and a temperature of 20C? What is the ratio of the kinematic viscosity of air to that of water for the same conditions?

At a point in a flowing fluid, the shear stress is l X 10- 4 psi, and the velocity gradient is l s-t. a. What is the viscosity in traditional units? b. Convert this viscosity to Sl units. c. Is this fluid more, or less, viscous than water?

SAE lOW-30 oil with viscosity 1 X I0- 4 lbf slfi is used as a lubricant between two parts of a machine that slide past one another with a velocity difference of 6 ft/s. What spacing, in inches, is required if you don't want a shear stress of more than 2lbf/tr?

The velocity distribution for the flow of crude oil at l00F (f.L = 8 X I 0-; lbf s/ft 2 ) between two walls is shown and is given by u = lOOy(O.l - y) ft/s, where y is measured in feet and the space between the walls is 0.1 ft. Plot the velocity distribution and determine the shear stress at the walls.

(part a only) A liquid flows between parallel boundaries as shown above. The velocity distribution near the lower wall is given in the following table: 0.0 0.00 1.0 1.00 2.0 1.99 3.0 2.98 a. If the viscosity of the liquid is 10- 3 N s/m2 , what is the maximum shear stress in the liquid? b. Where will the minimum shear stress occur?

Suppose that glycerin is flowing (T = 20C) and that the pressure gradient dpldx is - 1.6 kN/m3 What are the velocity and shear stress at a distance of 12 mm from the wall if the space B between the walls is 5.0 em? What are the shear stress and velocity at the wall? The velocity distribution for viscous flow between stationary plates is I dp u =---(By- y 2 ) 2f.L dx

Two plates are separated by a l/8-in. space. The lower plate is stationary; the upper plate moves at a velocity of 25 ft/s. Oil (SAE IOW-30, 150F), which fills the space between the plates, has the same velocity as the plates at the surface of contact. The variation in velocity of the oil is linear. What is the shear stress in the oil?

The sliding plate viscometer shown below is used to measure the viscosity of a fluid. The top plate is moving to the right with a constant velocity of lO m/s in response to a force of 3 N. The bottom plate is stationary. What is the viscosity of the fluid? Assume a linear velocity distribution. F _j_ lmmT PROBII:\1 2.35

A laminar flow occurs between two horizontal parallel plates under a pressure gradient dplds (p decreases in the positives direction). The upper plate moves left (negative) at elocity u,. The expression for local velocity u is given as 1 dp y u = - - (Hy - y2) + u,- 2f-L ds H a. ls the magnitude of the shear stress greater at the moving plate (y = H) or at the stationary plate (y = 0)? b. Derive an expression for they position of zero shear stress. c. Derive an expression for the plate speed u1 required to make the shear stress zero at y = 0.

This problem involves a cylinder falling inside a pipe that is 5lled with oil, as depicted in the figure. The small space between :he cylinder and the pipe is lubricated with an oil film that has -lSCosity IJ.. Derive a formula for the steady rate of descent of a ~ylinder with weight w; diameter d, and length e sliding inside a .certical smooth pipe that has inside diameter D. Assume that the cYlinder is concentric with the pipe as it falls. Use the general "Ormula to find the rate of descent of a cylinder 100 mm in diameter that slides inside a 100.5 mm pipe. The cylinder is 200 mm long Uld weighs 15 N. The lubricant is SA.E 20W oil at 10C.

The device shown consists of a disk that is rotated by .. shaft. The disk is positioned very close to a solid boundary. .;.etween the disk and the boundary is viscous oil. a. If the disk is rotated at a rate of 1 rad/s, what will be the ratio of the shear stress in the oil at r = 2 em to the shear stress at r = 3 em?b. If the rate of rotation is 2 rad/s, what b the speed of the oil in contact with the disk at r = 3 em? ' If the oil viscosity is 0.01 N s/m2 and the spacingy is 2 mm, what is the shear stress for the conditions noted in part (b)?

Some instruments having angular motion are damped by means of a disk connected to the shaft. The disk, in turn, is immersed in a container of oil, as shown. Derive a formula for the damping torque as a function of the disk diameter D, spacing S, rate of rotation w, and oil viscosity IJ..

If temperature increases, does the viscosity of water increase or decrease? Why? If temperature increases, does the viscosity of air increase or decrease? Why?

Sutherland's equation (select all that apply): a. relates temperature and viscosity b. must be calculated using Kelvin c. requires usc of a single universal constant for all gases d. requires use of a different constant for each gas

When looking up values for density, absolute viscosity, and kinematic viscosity, which statement is true for both liquids and gases? a. all three of these properties vary with temperature b. all three of these properties vary with pressure c. all three of these properties vary with temperature and pressure

Common Newtonian fluids are a. toothpaste, catsup, and paint b. water, oil, and mercury c. all of the above

Which of these flows (deforms) with even a small shear stress applied? a. a Bingham plastic b. a Newtonian fluid

Using Sutherland's equation and the ideal gas law, develop an expression for the kinematic viscosity ratio v/v0 in terms of pressures p and Po and temperatures T and T0, where the subscript 0 refers to a reference condition.

The dynamic viscosity of air at 15C is 1.78 X 10- 5 N s/m2 . Using Sutherland's equation, find the viscosity at 100C.

The kinematic viscosity of methane at 15C and atmospheric pressure is 1.59 X I o-s m2 /s. Using Sutherland's equation and the ideal gas law, find the kinematic viscosity at 200C and 2 atmospheres.

lhe dynamic viscosity of nitrogen at 59F is 3.59 X 10- 7 lbf s/ft2 . Using Sutherland's equation, find the dynamic viscosity at 200F.

Ammonia is very volatile, so it may be either a gas or a liquid at room temperature. When it is a gas, its absolute viscosity at 68F is 2.07 X I0- 7 1bf s/ft2 and at 392F is 3.46 X l0- 7 lbf s/ft2 Using these two data points, find Sutherland's constant for ammonia.

The viscosity of SAE 10W-30 motor oil at 38C is 0.067 N s/m2 and at 99C is 0.011 N s/m2 Using Eq. (2.20) (p. 42, 2.7) for interpolation, find the viscosity at 60C. Compare this value with that obtained by linear interpolation.

The viscosity of grade 100 aviation oil at 100F is 4.43 X 10 3 lbf s/ft2 and at 210F is 3.9 X 10 ' 1 lbf s/ft2 Using Eq. (2.20) (p. 42, 2.7), find the viscosity at 150F.

Find the kinematic and dynan1ic viscosities of air and water at a temperature of 40C (I 04F) and an absolute pressure of 170 kPa (25 psia).

Consider the ratio !l- 10oi ~L o. where 11- is the viscosity of oxygen and the subscripts I 00 and 50 are the temperatures of the oxygen in degrees Fahrenheit. Does this ratio have a value (a) less than 1, (b) equal to 1, or (c) greater than I?

Surface tension: (select all that apply) a. only occurs at an interface, or surface b. has dimensions of energy/area c. has dimensions of force/area d. has dimensions of force/length e. depends on adhesion and cohesion f. varies as a function of temperature

Which of the following is the formula for the gage pressure within a very small spherical droplet of water: (a) p = u /d, (b) p = 4u/d, or (c) p = 8u/d?

A spherical soap bubble has an inside radius R, a film thickness t, and a surface tension IT. Derive a formula for the pressure within the bubble relative to the outside atmospheric pressure. What is the pressure difference for a bubble with a 4 mm radius? Assume u is the same as for pure water.

A water bug is suspended on the surface of a pond by surface tension (water does not wet the legs). The bug has six legs, and each leg is in contact with the water over a length of 5 mm. What is the maximum mass (in grams) of the bug if it is to avoid sinking?

Calculate the maximum capillary rise of water between two certical glass plates spaced 1 mm apart.

What is the pressure within a 1 mm spherical droplet of a ter relative to the atmospheric pressure outside?

By measuring the capillary rise in a tube, one can calculate ;he surface tension. The surface tension of water varies linearly i th temperature from 0.0756 N/m at 0C to 0.0589 N/ m at l00C. Size a tube (specify diameter and length) that uses capillary rise of water to measure temperature in the range from _ c to I 00C. Is this design for a thermometer a good idea?

Capillary rise can be used to describe how far water ,[( rise above a water table because the interconnected pores in Jte soil act like capillary tubes. lhis means that deep-rooted :-!ants in the desert need only grow to the top of the "capillary Tinge" in order to get water; they do not have to extend all the "llY down to the water table. a. Assuming that interconnected pores can be represented as a continuous capillary tube, how high is the capillary rise in a soil consisting of a silty soil, with pore diameter of 10 J.UU? b. Is the capillary rise higher in a soil with fine sand (pore diam. approx. 0.1 mm), or in fine gravel (pore diam. approx. 3 mm)? c. Root cells extract water from soil using capillarity. For root cells to extract water from the capillary zone, do the pores in a root need to be smaller than, or greater than, the pores in the soil? Ignore osmotic eflects.

Consider a soap bubble 2 mm in diameter and a droplet of ..-ater, also 2 mm in diameter, that are falling in air. If the value of ;.'le surface tension for the film of the soap bubble is assumed to ~ the same as that for water, which has the greater pressure "lside it? (a) the bubble, (b) the droplet, (c) neither-the pressure the san1e for both.

A drop of water at 20C is forming under a solid surface. :he configuration just before separating and falling as a drop is own in the figure. Assume the forming drop has the volume of . hemisphere. What is the diameter of the hemisphere just before ;epa rating?

The surface tension of a liquid is being measured with a ring as shown. The ring has an outside diameter of 10 em and an inside diameter of9.5 em. The mass of the ring is 10 g. The force required to pull the riJ1g from the liquid is the weight corresponding to a mass of 16 g. What is the surface tension of the liquid (in N/m)?

If liquid water at 30C is flowing iJ1 a pipe and the pressure drops to the vapor pressure, what happens in the water? a. the water begins condensing on the walls of the pipe b. the water boils c. the water flashes to vapor

How does vapor pressure change with increasing temperature? a. it increases b. it decreases c. it stays the same

A student iJ1 the laboratory plans to exert a vacuum in the head space above a surface of water in a closed tank. She plans for the absolute pressure in the tank to be 10,400 Pa. The temperature in the lab is 20C. Will water bubble into the vapor phase under these circumstances?

The vapor pressure of water at I 00C is I 0 I kN/m2 because water boils under these conditions. The vapor pressure of water decreases approximately linearly with decreasing temperature at a rate of 3.1 kN!m2 rC. Calculate the boiling temperature of water at an altitude of 3000 m, where the atmospheric pressure is 69 kN/m2 absolute.