Deck 13: Fluids

Question 1

The buoyant force occurs because the pressure in a fluid increases with depth.

Answer 1

True

Question 2

State Pascal's Principle

Answer 2

If an external pressure is applied to a confined fluid, the pressure at every point within the fluid increases by that amount.

Question 3

Consider ice cubes floating in a glass of water. What will happen to the level of the water as the ice melts?

Answer 3

The water level remains unchanged since the ice displaces its own weight of water.

Question 4

Pressure in a fluid decreases with depth.

Question 5

Describe the two categories of pumps discussed in the text.

Question 6

State Archimedes' Principle.

Question 7

At any depth in a fluid at rest, the pressure is the same in all directions at the given depth.

Question 8

The specific gravity of a substance is the ratio of the density of that substance to the density of water at 6.0°C.

Question 9

The three common phases of matter are

A)solid, liquid, and gas.
B)solid, liquid, and vapor.
C)solid, fluid, and plasma.
D)solid, plasma, and gas.
E)condensate, plasma, and gas.

Question 10

If an external pressure is applied to a confined fluid, the pressure at every point within the fluid increases by that amount.

Question 11

State and describe the three phases of matter.

Question 12

State Bernoulli's principle.

Question 13

An object floats on a fluid if its density is less than that of the fluid.

Question 14

To determine gauge pressure, add the atmospheric pressure to the absolute pressure.

Question 15

The upward pressure on the bottom surface of a submerged object is less than the downward pressure on its top surface.

Question 16

What is meant by gauge pressure?

Question 17

Define specific gravity.

Question 18

The buoyant force acting on an object is equal to the weight of the object.

Question 19

A material that resists any type of stress applied to it when the magnitude of the stress does not exceed some limit is a

A)liquid.
B)solid.
C)gas.
D)liquid crystal.
E)fluid.

Question 20

Distinguish between laminar and turbulent flow of fluids.

Question 21

50 cm³ of wood is floating on water, and 50 cm³ of iron is totally submerged. Which has the greater buoyant force on it?

A)the wood
B)the iron
C)Both have the same buoyant force.
D)cannot be determined without knowing their densities

Question 22

Salt water is more dense than fresh water. A ship floats in both fresh water and salt water. Compared to the fresh water, the volume of water displaced in the salt water is

A)more.
B)less.
C)the same.
D)Cannot be determined from the information given.

Question 23

As a rock sinks deeper and deeper into water of constant density, what happens to the buoyant force on it?

A)It increases.
B)It remains constant.
C)It decreases.
D)It may increase or decrease, depending on the shape of the rock.
E)It may increase or decrease, depending on the weight of the rock.

Question 24

What is the difference between the pressures inside and outside a tire called?

A)absolute pressure
B)atmospheric pressure
C)fluid pressure
D)gauge pressure
E)N/m²

Question 25

An incompressible fluid flows irrotationally through a tube of circular crosssection that has greater diameter at one end than the other. What conclusion can you reach about the speed of the fluid at the ends of the tube?

A)The flow must be at a slower speed at the end with a greater diameter.
B)The speed of the flow must be the same at both ends.
C)Pressures and tube heights must be known to relate the flow speeds at the two ends.
D)The flow must be at a faster speed at the end with a greater diameter.
E)No conclusions can be reached based on this information.

Question 26

If a fluid does not change density as it moves, the fluid is undergoing

A)laminar flow.
B)turbulent flow.
C)irrotational flow.
D)steady flow.
E)incompressible flow.

Question 27

Salt water has greater density than fresh water. A boat floats in both fresh water and in salt water. Where is the buoyant force greater on the boat?

A)salt water
B)fresh water
C)Buoyant force is the same in both.
D)Cannot be determined from the information given.

Question 28

How a ship floats is described in terms of

A)Bernoulli's principle.
B)Pascal's principle.
C)Archimedes' principle.
D)Poiseuille's equation.
E)Torricelli's equation.

Question 29

When atmospheric pressure increases, what happens to the absolute pressure at the bottom of a pool?

A)It does not change.
B)It increases by a lesser amount.
C)It increases by the same amount.
D)It increases by a greater amount.
E)It depends on the depth of the pool.

Question 30

The hydraulic lift is an application of

A)Bernoulli's principle.
B)Pascal's principle.
C)Archimedes' principle.
D)Poiseuille's equation.
E)Torricelli's equation.

Question 31

A piece of iron rests on top of a piece of wood floating in a bathtub. If the iron is removed from the wood, what happens to the water level in the tub?

A)It goes up.
B)It goes down.
C)It does not change.
D)cannot be determined from the information given

Question 32

"An external pressure applied to an enclosed fluid is transmitted unchanged to every point within the fluid" is known as

A)Archimedes' principle.
B)Bernoulli's principle.
C)Torricelli's law.
D)Pascal's principle.
E)Fermat's principle.

Question 33

Consider three drinking glasses. All three have the same area base, and all three are filled to the same depth with water. Glass A is cylindrical. Glass B is wider at the top than at the bottom, and so holds more water than A. Glass C is narrower at the top than at the bottom, and so holds less water than A. Which glass has the greatest liquid pressure at the bottom?

A)Glass A
B)Glass B
C)Glass C
D)All three have equal non-zero pressure at the bottom.
E)All three have zero pressure at the bottom.

Question 34

A cup of water is filled to the brim when an ice cube is placed in it. The tip of the ice cube sticks out of the surface. As the ice melts, you observe that

A)the cup overflows.
B)the cup might overflow but it depends on the actual mass of the ice cube.
C)the water level remains the same.
D)the water level actually goes down.
E)There is not enough information to answer this question.

Question 35

If all fluid flow within a volume of fluid can be traced as streamlines, the fluid flow is

A)turbulent flow.
B)incompressible flow.
C)nonviscous flow.
D)laminar flow.
E)irrotational flow.

Question 36

You have two identical pure silver ingots. You place one of them in a glass of water and observe it to sink to the bottom. You place the other in a container full of mercury and observe that it floats. Comparing the buoyant forces in the two cases you conclude that

A)the buoyant force in the water is equal to that in mercury.
B)the buoyant force in the water is larger than that in mercury.
C)the buoyant force in water is smaller than that in mercury.
D)the buoyant force in the water is zero and that in mercury is non-zero.
E)No conclusion can be made about the respective values of the buoyant forces.

Question 37

Is the mass of iron greater than, less than, or equal to the mass of aluminum?

A)The mass of iron is equal to the mass of aluminum.
B)The mass of iron is greater than the mass of aluminum.
C)The answer depends on temperature.
D)This is an incorrectly stated question. Iron and aluminum are types of material, mass is the property of an object.
E)The mass of iron is less than the mass of aluminum.

Question 38

You are originally 1.0 m beneath the surface of a pool. If you dive to 2.0 m beneath the surface, what happens to the absolute pressure on you?

A)It quadruples.
B)It more than doubles.
C)It doubles.
D)It less than doubles.
E)It does not change.

Question 39

A piece of wood is floating in a bathtub. A second piece of wood sits on top of the first piece, and does not touch the water. If the top piece is taken off and placed in the water, what happens to the water level in the tub?

A)It goes up.
B)It goes down.
C)It does not change.
D)cannot be determined from the information given

Question 40

At a fixed depth within a fluid at rest, the pressure pushing upward is

A)less than the pressure pushing downward.
B)zero, because pressure only pushes equal in all horizontal direction.
C)zero, because the fluid above does not support the weight of the fluid below.
D)greater than the pressure pushing downward.
E)equal to the pressure pushing downward.

Question 41

A U-tube with a cross-sectional area of 1.00 cm² is open to the atmosphere at both ends. Water is poured into the tube until the water rises part-way along the straight sides, and then 5.00 cm³ of oil is poured into one end. As a result, the top surface of the oil ends up 0.550 cm higher than the water surface on the other side of the U. What is the density of the oil?

Question 42

When you blow some air above a paper strip, the paper rises. This is because

A)the air above the paper moves faster and the pressure is higher.
B)the air above the paper moves faster and the pressure is lower.
C)the air above the paper moves faster and the pressure remains constant.
D)the air above the paper moves slower and the pressure is higher.
E)the air above the paper moves slower and the pressure is lower.

Question 43

On planet X, the pressure at a depth of 2.00 m below the surface of a liquid nitrogen lake is 5.00 × 10⁵ N/m². At a depth 5.00 m below the surface, the pressure is 8.00 × 10⁵ N/m². The density of liquid nitrogen is 808 kg/m³.
(a) What is the atmospheric pressure at the surface of the lake?
(b) What is the acceleration of gravity on planet X?

Question 44

A solid right circular cylinder of a substance has a radius 10.0 cm and a height 12.0 cm. The mass of the cylinder is 4.00 kg. What is the density of the substance?

A)1.59 × 10³ kg/m³
B)1.33 × 10³ kg/m³
C)2.12 × 10³ kg/m³
D)1.86 × 10³ kg/m³
E)1.06 × 10³ kg/m³

Question 45

An object moves with constant speed through a fluid. For a fixed geometry and fluid density, if the viscosity of the fluid increases then the speed at which flow becomes turbulent

A)increases.
B)remains the same.
C)decreases.
D)could increase or decrease depending on the shape of the object.
E)could increase or decrease depending on the value of the fluid density.

Question 46

The fact that a dew drop is spherical is best described in terms of

A)gravitation.
B)gauge pressure.
C)surface tension.
D)Archimedes' principle.
E)viscosity.

Question 47

A valve is closed and the fluid within a pipe is stationary. When the valve is opened, fluid flows through the pipe. What happens to the pressure in the pipe when the valve is opened?

A)The direction of the pressure change depends on the direction of the fluid flow.
B)The direction of the pressure change depends on the density of the fluid.
C)The pressure decreases.
D)The pressure increases.
E)The pressure remains the same.

Question 48

The lift on an airplane wing is an application of

A)Bernoulli's principle.
B)Pascal's principle.
C)Archimedes' principle.
D)Poiseuille's equation.
E)Torricelli's equation.

Question 49

Bernoulli's principle is a statement of the

A)conservation of linear momentum.
B)conservation of mass.
C)conservation of energy.
D)conservation of kinetic energy.
E)conservation of angular momentum.

Question 50

A sphere is constructed of two concentric pieces. The inner part is a solid sphere of radius 10.0 cm made of a material with density 4000 kg/m³. The outer part is a spherical shell with inner radius 10.0 cm and outer radius 20.0 cm. The outer shell has a density 9000 kg/m³.
(a) What is the mass of this sphere?
(b) What is the average density of this sphere?

Question 51

The pressure drop in a tube carrying a viscous fluid is described by

A)Bernoulli's principle.
B)Pascal's principle.
C)Archimedes' principle.
D)Poiseuille's equation.
E)Newton's Second law.

Question 52

A piece of aluminum with a mass of 1.0 kg and density of 2700 kg/m³ is suspended from a string and then completely immersed in a container of water. The density of water is 1000 kg/m³.
(a) Determine the volume of the piece of aluminum.
(b) Determine the tension in the string after the metal is immersed in the container of water.

Question 53

The small piston of a hydraulic lift has a diameter of 8.0 cm, and its large piston has a diameter of 40 cm. The lift raises a load of 15,000 N.
(a) Determine the force that must be applied to the small piston.
(b) Determine the pressure applied to the fluid in the lift.

Question 54

You are driving a late model convertible at the 55 mph limit with its soft ragtop roof up and the windows closed. You observe that the roof

A)bows inward.
B)is not changed from when the car was at rest.
C)bows outward.
D)bows inward only when you are driving uphill.
E)bows inward only when you are driving downhill.

Question 55

The fact that a pin placed carefully on the surface of the water can remain there without sinking is best explained by

A)gravitation.
B)gauge pressure.
C)surface tension.
D)Archimedes' principle.
E)viscosity.

Question 56

As the speed of a moving fluid increases, the pressure in the fluid

A)increases.
B)remains constant.
C)decreases.
D)may increase or decrease, depending on the viscosity.

Question 57

A 1938-nickel has a diameter of 21.21 mm, a thickness of 1.95 mm, and weighs 0.04905 N. What is its density?

A)29.1 × 10³ kg/m³
B)7.26 × 10³ kg/m³
C)9.25 × 10³ kg/m³
D)2.31 × 10³ kg/m³
E)71.2 × 10³ kg/m³

Question 58

The equation of continuity is a statement of which conservation rule applied to fluids in steady laminar flow?

A)conservation of area
B)conservation of volume
C)conservation of energy
D)conservation of momentum
E)conservation of mass

Question 59

A sphere of radius 10.0 cm floats in equilibrium partially submerged in water with its lowest point 5.00 cm below the water's surface.
(a) What is the buoyant force acting on the sphere?
(b) What is the weight of the sphere?

Question 60

The pressure differential across a wing cross section due to the difference in air flow is explained by

A)Pascal's Principle.
B)Bernoulli's equation.
C)Poiseuille's law.
D)Archimedes Principle.
E)Torricelli's law.

Question 61

A liquid has a specific gravity of 0.68. What is its density?

A)680 kg/m³
B)1360 kg/m³
C)1000 kg/m³
D)6800 kg/m³

Question 62

A 12000-N car is raised using a hydraulic lift, which consists of a U-tube with arms of unequal areas, filled with oil with a density of 800 kg/m³ and capped at both ends with tight-fitting pistons. The wider arm of the U-tube has a radius of 18.0 cm and the narrower arm has a radius of 5.00 cm. The car rests on the piston on the wider arm of the U-tube. The pistons are initially at the same level. What is the force that must be applied to the smaller piston in order to lift the car after it has been raised 1.20 m? For purposes of this problem, neglect the weight of the pistons.

A)0.954 kN
B)1.88 kN
C)1.96 kN
D)3.67 kN
E)1.20 kN

Question 63

A 100-kg person sits on a 5-kg bicycle. The weight is borne equally by the two wheels of the bicycle. The tires are inflated to a gauge pressure of 8.0 × 10⁵ Pa and are 2.0 cm wide. What length of each tire is in contact with the ground?

A)1.6 cm
B)1.8 cm
C)3.2 cm
D)2.4 cm
E)6.4 cm

Question 64

How much force acts on one surface of a rectangular bedroom wall that is 2.20 m by 3.20 m when atmospheric pressure is 1.00 × 10⁵ N/m² ?

A)3.52 × 10⁵ N
B)1.78 × 10⁵ N
C)1.45 × 10⁵ N
D)6.88 × 10⁴ N
E)7.04 × 10⁵ N

Question 65

What is the gauge pressure if the absolute pressure is 300 kPa?

A)97 kPa
B)101 kPa
C)199 kPa
D)150 kPa
E)300 kPa

Question 66

A platinum sphere has a radius of 1.20 cm. The density of platinum is 21.4×10³ kg/m³. What is the mass of the sphere?

A)37.0 g
B)38.7 g
C)69.3 g
D)21.4 g
E)155 g

Question 67

A U-tube is open to the atmosphere at both ends. Water is poured into the tube until the water rises part-way along the straight sides, and then some oil with a density of 920 kg/m³ is poured into one end. This causes the water surface on that side of the tube to go down by 5.50 mm, and the surface on the other side to go up by the same amount. How much higher is the top surface of the oil on that side of the tube compared with the surface of the water on the other side of the tube?

A)0.96 mm
B)1.2 mm
C)0.44 mm
D)1.2 cm
E)1.1 cm

Question 68

The Aswan High Dam is 111 m high. What is the water pressure at the foot of the dam?

A)1.09 k Pa
B)0.111 k Pa
C)0.111 M Pa
D)1.09 M Pa
E)111 Pa

Question 69

A cubical box, 5.00 cm on each side, is immersed in a fluid. The pressure at the top surface of the box is 594 Pa and the pressure on the bottom surface is 1133 Pa. What is the density of the fluid?

A)1,000 kg/m³
B)1,100 kg/m³
C)1,220 kg/m³
D)2,340 kg/m³
E)12,000 kg/m³

Question 70

A U-tube is open to the atmosphere at both ends. Water is poured into the tube until the water column on the vertical sides of the U is more than 10 cm deep. Then, oil with a density of 950 kg/m³ is poured into one side, until the column of oil is 6.0 cm tall. How much higher is the top surface of the oil on that side of the tube compared with the surface of the water on the other side of the tube?

A)3.1 cm
B)2.9 cm
C)60 mm
D)3.0 mm
E)5.7 cm

Question 71

What is the absolute pressure at a distance 5.00 m below the surface of a lake? Assume the density of the water in the lake is 1000 kg/m³.

A)5.00 × 10³ N/m²
B)1.50 × 10⁵ N/m²
C)0.49 × 10⁵ N/m²
D)1.05 × 10⁵ N/m²
E)4.66 × 10⁵ N/m²

Question 72

What is the radius of a sphere that has a density 5000 kg/m³ and a mass 6.00 kg?

A)4.98 cm
B)1.27 m
C)6.59 cm
D)1.56 m
E)7.22 cm

Question 73

A basketball player pushes down with a force of 50 N on a basketball that is inflated to a gauge pressure of 8.0 × 10⁴ Pa. What is the diameter of contact between the ball and the floor?

A)2.8 cm
B)1.4 cm
C)1.7 cm
D)2.1 cm
E)5.6 cm

Question 74

The deepest point of the Pacific Ocean is 11,033 m, in the Mariana Trench. What is the water pressure at that point? The density of seawater is 1025 kg/m³.

A)1.13 × 10⁷ Pa
B)2.18 × 10⁵ Pa
C)1.11 × 10⁴ Pa
D)1.11 × 10⁸ Pa
E)1.09 × 10⁵ Pa

Question 75

A 12000-N car is raised using a hydraulic lift, which consists of a U-tube with arms of unequal areas, filled with oil and capped at both ends with tight-fitting pistons. The wider arm of the U-tube has a radius of 18.0 cm and the narrower arm has a radius of 5.00 cm. The car rests on the piston on the wider arm of the U-tube. The pistons are initially at the same level. What is the initial force that must be applied to the smaller piston in order to start lifting the car? For purposes of this problem, neglect the weight of the pistons.

A)727 N
B)926 N
C)2900 N
D)3330 N
E)1.20 kN

Question 76

The weight of a 1200-kg car is supported equally by the four tires, which are inflated to the same gauge pressure. What gauge pressure is required so the area of contact of each tire with the road is 100 cm²?

A)11.6 × 10⁵ Pa
B)11.6 × 10⁴ Pa
C)2.9 × 10⁵ Pa
D)2.9 × 10⁴ Pa
E)2.9 × 10³ Pa

Question 77

A 13000 N vehicle is to be lifted by a 25 cm diameter hydraulic piston. What force needs to be applied to a 5.0 cm diameter piston to accomplish this?

A)260 N
B)520 N
C)2600 N
D)5200 N
E)13000 N

Question 78

A 500-N weight sits on the small piston of a hydraulic machine. The small piston has area 2.0 cm². If the large piston has area 40 cm², how much weight can the large piston support?

A)25 N
B)500 N
C)1000 N
D)10000 N
E)40000 N

Question 79

A 1959 penny has a diameter of 19.55 mm, a thickness of 1.55 mm, and a mass of 2.500 g. What is its density?

A)5.37 × 10³ kg/m³
B)21.5 × 10³ kg/m³
C)1.34 × 10³ kg/m³
D)2.68 × 10³ kg/m³
E)1.86 × 10^-4 kg/m³

Question 80

What is the mass of a solid sphere that has a density 15.0 × 10³ kg/m³ and a radius 10.0 cm?

A)62.8 kg
B)4.56 kg
C)298 kg
D)3.58 × 10⁶ kg
E)15.0 kg