Chapter 9 Physics

An ideal barometer filled with an unknown liquid is used to measure atmospheric pressure. If the height of the fluid in the tube is 1.00 m and the pressure of the air is 1.00 atmosphere, then what is the density of the fluid in the tube? Use g = 9.80 m/s2.

10,300 kg/m3

Rank the following pressures, with the largest pressure at the top and the smallest at the bottom.

101.3 atm 1 atm 1013 Pa 1 Pa

Four identical cylinders are held underwater in different orientations, as shown. Consider the forces due to the fluid acting on the end of each cylinder indicated by the circle. From the list below, match each case with the direction of the fluid force acting.

B--> up C--> left D--> right A--> down

What kind of motion does an ideal fluid flow follow?

Laminar

Rank the following substances according to their specific gravity, with the largest specific gravity at the top and the smallest at the bottom. Assume that all of the substances are at atmospheric pressure.

Solid granite Liquid water at 3.98 degrees C Liquid water at 0 degrees C Helium gas Hydrogen gas

Select all of the following that correctly describe manometers.

The difference in the fluid levels is a measure of the pressure difference. They are used to measure the pressures of gases. They are U-shaped tubes.

Assume that a static fluid is confined in a container and completely fills the container. The pressure of the fluid at the top of the container decreases. Select all of the following statements that are true.

The pressure of the fluid in the middle of the container decreases by the same amount. The pressure of the fluid at the bottom of the container decreases by the same amount.

Assume that a static fluid is confined in a container and completely fills the container. The pressure of the fluid at the top of the container increases. Select all of the following statements that are true.

The pressure of the fluid in the middle of the container increases by the same amount. The pressure of the fluid at the bottom of the container increases by the same amount.

A manometer is connected on the left to a container filled with a gas, and on the right it is open to the atmosphere. The fluid level on the left side of the manometer is lower than the fluid level on the right side. Which statement is true?

The pressure of the gas in the container is greater than atmospheric pressure.

A manometer is connected on the left to a container filled with a gas, and on the right it is open to the atmosphere. The fluid level on the left side of the manometer is higher than the fluid level on the right side. Which statement is true?

The pressure of the gas in the container is less than atmospheric pressure.

What is an equivalent way to think of volume flow rate?

The rate at which a volume changes

What is a drag force?

The resistive force on an object moving through a fluid

For an underwater air bubble in equilibrium, choose which quantities the excess pressure depends on.

The surface tension of the liquid The volume of the bubble The radius of the bubble

What are the SI units of density?

kg/m3

What are the SI units of volume flow rate?

m3/s

Four containers with varying diameters at the bottom surfaces are filled to the same height with water, as shown. The upper surface of the water is at atmospheric pressure for all containers. Select the correct ranking of the pressures on the bottom surfaces of the containers.

pA = pB = pC = pD

A barometer is a manometer used to measure atmospheric _____ .

pressure

Four cylindrical beakers are partially filled with water. The radii of the beakers and the heights to which each is filled with water are given below. Rank the beakers according the gauge pressure on the bottom of the beakers, with the largest gauge pressure at the top of the list and the smallest at the bottom of the list.

r= 5.0cm, h= 5.0 cm r= 6.0 cm, h= 3.0 cm r= 10.0 cm, h= 2.0 cm r= 8.0cm, h= 1.0 cm

A capillary carries blood in the direction shown. Viscosity is not negligible. Points C and D are on the central axis of the capillary. Which of the following is the correct ranking of the speeds of the fluid?

vC = vD > vB > vA

Two coins A and B rest on the bottom of a swimming pool. The diameter of coin B is twice that of coin A. The water exerts a downward force on the upper surface of each coin. By what factor is the magnitude of the downward force on B larger than that on A?

4

You suspect some air has gotten into the evacuated portion of your mercury barometer because the level is lower than it should be. If the mercury column is only 70 cm tall what is the absolute pressure in the supposedly evacuated portion? Assume the atmospheric pressure to be 1.00 atm.

0.079 atm

Water is flowing through a horizontal pipe whose diameter varies, but the elevation of the pipe is constant. The pressure is measured at four different points along the pipe (p0 = 1 atm). Rank the speeds of the water at the four points where the pressure is measured, with the largest speed at the top and the smallest at the bottom.

0.75p0 p0 1.5p0 2p0

A section of a pipe filled with moving water is shown in the figure. Rank the pressure at the three points shown, with the greatest pressure at the top and the smallest at the bottom. Assume that the diameters of the pipe at points 1 and 2 are equal.

3 2 1

Select all of the following statements that are true.

Density is inversely proportional to volume. Density is directly proportional to mass.

Which of the following would double the flow rate of a viscous fluid through a pipe?

Double the pressure difference

What is turbulence?

Extreme example of unsteady flow

Select the correct ranking of the magnitudes of the four forces that are required to balance the loads shown in the figure. Assume that the piston diameters are the same in all cases.

F4 > F3 = F2 > F1

Select all of the following statements that are true regarding the effects of the Earth's atmospheric pressure on objects on or near the surface of the Earth.

In living organisms, atmospheric pressure is matched by the pressure inside cells. In most situations, atmospheric pressure cannot be ignored because it is relatively large.

Select all of the following that are possible units of pressure.

Inches of mercury Millimeters of mercury

A water company wants to increase the amount of water it can deliver to a city. What can it do to increase the mass flow rate? Treat the water as an ideal fluid.

Increase the speed at which the water moves Increase the diameter of the water main

Which of the following are not units of pressure?

Nm2 N/m

In which of the following situations would Bernoulli's equation be valid?

Oil moving slowly through a thin tube

In which direction is the force of a static fluid on the walls of a container?

Outward

Select all of the following substances whose densities could decrease significantly when the temperature increases by a relatively small amount. Assume that the substances are not confined by any sort of container.

Oxygen gas Carbon dioxide gas

Which of the following are the SI units of pressure?

Pa

Select all of the following that are units of viscosity.

Pa⋅s kgm⋅s N⋅sm2

What is the magnitude of the average momentum of the atoms or molecules in a static fluid?

Zero

Three different companies are competing for a contract to install liquid nitrogen delivery systems for a laboratory. Rank the following deliver systems according to the mass flow rate from greatest to least starting with the greatest. Assume they all use the same temperatures (so the density is the same) and you should treat the nitrogen fluid as ideal.

Pipe diameter 3.0 cm and flow speed 6.0m/s Pipe diameter 6.0 cm and flow speed 6.0m/s Pipe diameter 3.0 cm and flow speed 12.0m/s

In the United States, which units are typically used to measure the pressure of air in tires?

Pounds per square inch

In a physics experiment, three identical steel balls are submerged in three different liquids (X, Y, and Z), as shown. In each instance, the scale reading is indicated. Rank the three liquids according their densities, with the largest density at the top and the smallest at the bottom.

Pz Py Px

Select all of the following that are always true for laminar fluid flow.

The fluid moves along streamlines. It is steady.

Select the true statement about viscous fluid flow in a pipe.

The pressure decreases along the direction of motion.

The parallel component cancels out due to the random orientation of the motion of the atoms and molecules.

The juice pushes to the right on the right side of the can. The juice pushes to the left on the left side of the can.

A solid object is completely submerged in a fluid. Which of the following would change the magnitude of the buoyant force exerted by the fluid on the solid object? Assume that the densities of the fluid and the solid object are constant in every case.

The volume of the solid object increases. The mass of the solid object decreases.

Select all of the following that correctly describe barometers.

They are used to measure atmospheric pressure. The difference in the fluid levels is a measure of atmospheric pressure.

What is the term for a drag force exerted by a fluid while the fluid flow remains laminar?

Viscous

Which of the following quantities is always constant for an incompressible liquid?

Volume

Select all of the following that are always constant for an ideal fluid. Assume that the mass of the fluid does not change.

Volume Density

An experiment involving three identical objects and three different liquids (X, Y, and Z) is conducted with the results shown in the figure. Rank the densities of the three liquids, with the greatest density at the top and the smallest at the bottom.

Z Y X

Select all of the following pressures that are approximately equal to the pressure of the Earth's atmosphere on or near its surface.

10 N/cm2 15 lb/in2

Select all of the following that are always true for an ideal fluid.

Constant volume Nonviscous

Liquid water at 4 degrees Celsius moves through a pipe 10 m long and 40 cm2 wide at 10 m/s. What is its mass flow rate if the flow is steady?

40 kg/s

The volume flow rate of a viscous fluid through a pipe is 80 m3/s. If the width of the pipe was halved and its length and the pressure difference between its ends remained the same, then what would be the volume flow rate?

5 m3/s

You have the capability of applying up to 150 N of force, but you need to raise up 900 N of load bearing weight. If you are going to design a hydraulic system to do this, what is the ratio of the area of the load bearing piston to the area of the applied force piston?

6

Three objects are at rest in a container of water as shown in the figure. Let the weight and cross-sectional area of each object be denoted by W1, W2, and W3 and A1, A2, and A3, respectively. Assume the height of each object is the same. Under which of the following conditions is this situation possible?

A1 = A2 = A3 and W1 > W2 > W3 A1 < A2 < A3 and W1 = W2 = W3.

Select all of the following that are scalars.

Area Pressure

What causes the pressure of a static fluid in a container?

Collisions of the atoms or molecules of the fluid

Four containers with varying diameters at the bottom surfaces are filled to the same height with water, as shown. Select the correct ranking of the magnitudes of the fluid forces on the bottom surfaces.

FA = FD > FB = FC

A cube is sinking in a beaker of water. Select the correct ranking according to the magnitude of the buoyant force acting on the cube at the three different depths indicated in the figure.

FB1 = FB2 = FB3

If the gauge pressure of a gas is halved, then what will always happen to its absolute pressure?

It will decrease.

Which size of bubble needs the most pressure to maintain equilibrium?

Smaller bubbles

A barometer is open to the atmosphere on one side. Why is the fluid level on the other side of the barometer higher than the fluid level on the side that is open to the atmosphere?

The atmosphere is pushing the fluid up.

Select all of the following that are always true for steady fluid flow.

The density of the fluid at any one point is constant. The pressure of the fluid at any one point is constant. The velocity of the fluid at any one point is constant.

Why are ordinary containers not crushed by the force from atmospheric pressure?

The pressure inside the containers approximately matches atmospheric pressure resulting a net zero force.

Select all of the following that are always true for steady fluid flow.

The pressure of the fluid at any one point is constant. The density of the fluid at any one point is constant. The velocity of the fluid at any one point is constant.

Select the correct ranking of the fluid pressures at the points indicated in the image.

pD > pC = pE > pB > pA

Which quantities are neglected in Bernoulli's equation by considering only ideal fluid flow?

Turbulence Viscosity

A cross-sectional view of an ideal fluid flowing in a tube is shown in the figure. Rank the fluid flow speeds v1, v2, and v3, with the largest fluid flow speed at the top and the smallest at the bottom.

V2 V1 V3

Which of the following would cut in half the flow rate of a viscous fluid through a pipe.

Double the viscosity Double the length

Four mercury barometers are kept at sea level. However, unlike in an ideal barometer, the air gap above the mercury column of these four barometers has not been completely evacuated. Because of this, the heights of the mercury columns are different in each case, as indicated in the image. Rank these according to the pressure of the gas trapped above the mercury column in the tube, with the smallest pressure at the top and the largest pressure at the bottom.

Barometer A : h= 760 mm Barometer C : h= 720 mm Barometer B : h= 360 mm Barometer D : h= 240 mm

Select all of the following statements that are true regarding the specific gravity of a substance.

It is directly proportional to the density of the substance. It has no units.

A hot-air balloon is moving downward at constant speed. Which of the following statements is correct regarding the density of the air inside the balloon? (Assume the mass of the balloon itself is zero.)

It is equal to the density of the air outside the balloon.

Which are true about viscous drag?

It occurs for low speeds. It happens when the fluid flow around the object is laminar. It is proportional to the speed of the object.

A student is conducting an experiment in which an ideal fluid flows from point A to point B in a pipe. In one of the experiments, she notices that as the ideal fluid flows from A to B, the height of the pipe decreases, and the cross-sectional area does not change. What happens to the speed of ideal fluid as it flows from A to B?

It stays the same.

If the gauge pressure of a gas doubles, then what will always happen to its absolute pressure?

It will increase.

Select all of the following that are fluids.

Liquids and gasses

Match the three basic states of matter in the left column with their defining properties in the right column. Solid Liquid Gas

Solid --> (1) nearly incompressible; (2) needs no container, defines its own shape and volume Liquid --> (1) nearly incompressible; (2) shape determined by container, but not volume Gas --> (1) compressible; (2) shape and volume determined by container, always fills entire volume of container

Why is the net force due to the pressure exerted by a fluid perpendicular to the surface it is exerted on?

The parallel component cancels out due to the random orientation of the motion of the atoms and molecules.

Select all of the following statements that are true regarding a closed metal can containing fruit juice. Assume that the can is completely filled with juice and that the pressure of the fluid is greater than zero everywhere in the can.

The juice pushes up on the top of the can. The juice pushes down on the bottom of the can.

Select all of the following statements that are true regarding an underwater air bubble in equilibrium that is neither expanding nor contracting.

The magnitude of the sum of the forces on the bubble is equal to zero. The pressure inside the bubble is greater than the pressure outside the bubble.

If an object is made of a material with a specific gravity < 1, which statement is true.

The object weighs less than an amount of water that takes up the same volume. The object takes up more space than the same mass of water.

Assume that a fluid is confined in a container and completely fills the container. A force is applied to the sides of the container such that it is squeezed in a little in the middle. Select all of the following statements that are true.

The pressure of the fluid in the middle of the container increases. The pressure of the fluid at the top of the container increases. The pressure of the fluid at the bottom of the container increases.

Six cylinders with the same heights but with varying diameters are submerged to the same depth in water, as shown. Select the correct ranking of the pressures on the bottom surfaces.

pE = pD = pC = pB = pA ≠ 0