A long horizontal tube has a square cross section with

What is a fluid?

What is pressure?

What is buoyancy?

How does a fluid flow?

What is elasticity?

Why are fluids important?

What is the mass of air in a living room with dimensions 4.0 m * 6.0 m * 2.5 m?

A piece of glass is broken into two pieces of different size. Rank in order, from largest to smallest, the mass densities of pieces a, b, and c.

A 10.0-cm-diameter suction cup is pushed against a smooth ceiling. What is the maximum mass of an object that can be suspended from the suction cup without pulling it off the ceiling? The mass of the suction cup is negligible

Water is slowly poured into the container until the water level has risen into tubes A, B, and C. The water doesnt overflow from any of the tubes. How do the water depths in the three columns compare to each other? a. dA 7 dB 7 dC b. dA 6 dB 6 dC c. dA = dB = dC d. dA = dC 7 dB

A submarine cruises at a depth of 300 m. What is the pressure at this depth? Give the answer in both pascals and atmospheres.

Rank in order, from largest to smallest, the magnitudes of the forces F u a, F u b, and F u c required to balance the masses. The masses are in kilograms, the three smaller cylinders have the same diameter, and the four larger cylinders have the same diameter.

Water fills the tube shown in Figure 14.12. What is the pressure at the top of the closed tube?

An ice cube is floating in a glass of water that is filled entirely to the brim. When the ice cube melts, the water level will a. Fall. b. Stay the same, right at the brim. c. Rise, causing the water to spill.

An underwater pressure gauge reads 60 kPa. What is its depth?

The figure shows volume flow rates (in cm3 /s) for all but one tube. What is the volume flow rate through the unmarked tube? Is the flow direction in or out?

The pressure of a gas cell is measured with a mercury manometer. The mercury is 36.2 cm higher in the outside arm than in the arm connected to the gas cell. a. What is the gas pressure? b. What is the reading of a pressure gauge attached to the gas cell?

Rank in order, from highest to lowest, the liquid heights ha to hd. The airflow is from left to right

The hydraulic lift at a car repair shop is filled with oil. The car rests on a 25-cm-diameter piston. To lift the car, compressed air is used to push down on a 6.0-cm-diameter piston. What does the pressure gauge read when a 1300 kg car is 2.0 m above the compressed-air piston?

A 10 cm * 10 cm * 10 cm block of wood with density 700 kg/m3 is held underwater by a string tied to the bottom of the container. What is the tension in the string?

You need to determine the density of an unknown liquid. You notice that a block floats in this liquid with 4.6 cm of the side of the block submerged. When the block is placed in water, it also floats but with 5.8 cm submerged. What is the density of the unknown liquid?

A 20-m-wide, 4.0-m-deep river with a triangular cross section flows at a lazy 1.0 m/s. As it makes its way to the sea, the river enters a gorge where rocky walls confine it to a width of 4.0 m and a depth of 6.0 m, again with a triangular cross section. What is the rivers volume flow rate? And what is its speed through the gorge?

Water flows through the pipes shown in Figure 14.28. The waters speed through the lower pipe is 5.0 m/s and a pressure gauge reads 75 kPa. What is the reading of the pressure gauge on the upper pipe?

Small hydroelectric plants in the mountains sometimes bring the water from a reservoir down to the power plant through enclosed tubes. In one such plant, the 100-cm-diameter intake tube in the base of the dam is 50 m below the reservoir surface. The water drops 200 m through the tube before flowing into the turbine through a 50-cm-diameter nozzle. a. What is the water speed into the turbine? b. By how much does the inlet pressure differ from the hydrostatic pressure at that depth?

A \(2.0m\)-long, \(1.0mm\) diameter wire is suspended from the ceiling. Hanging a \(4.5 kg\) mass from the wire stretches the wire's length by \(1.0 mm\). What is Young's modulus for this wire? Can you identify the material?

A 1.00-m-diameter solid steel sphere is lowered to a depth of 10,000 m in a deep ocean trench. By how much does its diameter shrink?

A conical tank of radius R and height H, pointed end down, is full of water. A small hole of radius r is opened at the bottom of the tank, with r V R so that the tank drains slowly. Find an expression for the time T it takes to drain the tank completely

An object has density r. a. Suppose each of the objects three dimensions is increased by a factor of 2 without changing the material of which the object is made. Will the density change? If so, by what factor? Explain. b. Suppose each of the objects three dimensions is increased by a factor of 2 without changing the objects mass. Will the density change? If so, by what factor? Explain.

Rank in order, from largest to smallest, the pressures at a, b, and c in FIGURE Q14.2. Explai

Rank in order, from largest to smallest, the pressures at d, e, and f in FIGURE Q14.2. Explain

FIGURE Q14.4 shows two rectangular tanks, A and B, full of water. They have equal depths and equal thicknesses (the dimension into the page) but different widths. a. Compare the forces the water exerts on the bottoms of the tanks. Is FA larger than, smaller than, or equal to FB? Explain. b. Compare the forces the water exerts on the sides of the tanks. Is FA larger than, smaller than, or equal to FB? Explain.

In FIGURE Q14.5, is pA larger than, smaller than, or equal to pB? Explain

Rank in order, from largest to smallest, the densities of blocks a, b, and c in FIGURE Q14.6. Explain.

Blocks a, b, and c in FIGURE Q14.7 have the same volume. Rank in order, from largest to smallest, the sizes of the buoyant forces Fa, Fb, and Fc on a, b, and c. Explain

Blocks a, b, and c in FIGURE Q14.7 have the same density. Rank in order, from largest to smallest, the sizes of the buoyant forces Fa, Fb, and Fc on a, b, and c. Explain

The two identical beakers in FIGURE Q14.9 are filled to the same height with water. Beaker B has a plastic sphere floating in it. Which beaker, with all its contents, weighs more? Or are they equal? Explain

Gas flows through the pipe of FIGURE Q14.10. You cant see into the pipe to know how the inner diameter changes. Rank in order, from largest to smallest, the gas speeds va, vb, and vc at points a, b, and c. Explain.

Wind blows over the house in FIGURE Q14.11. A window on the ground floor is open. Is there an airflow through the house? If so, does the air flow in the window and out the chimney, or in the chimney and out the window? Explain.

A 2000 N force stretches a wire by 1 mm. A second wire of the same material is twice as long and has twice the diameter. How much force is needed to stretch it by 1 mm? Explain.

A wire is stretched right to the breaking point by a 5000 N force. A longer wire made of the same material has the same diameter. Is the force that will stretch it right to the breaking point larger than, smaller than, or equal to 5000 N? Explain.

What is the volume in mL of 55 g of a liquid with density 1100 kg/m3 ?

Cylinders A and B have equal heights. Cylinder A is filled with helium gas at 1.0 atm pressure and 0C. The diameter of cylinder B is half that of cylinder A, and cylinder B is filled with glycerin. What is the ratio of the fluid mass in cylinder B to that in cylinder A?

a. 50 g of gasoline are mixed with 50 g of water. What is the average density of the mixture? b. 50 cm3 of gasoline are mixed with 50 cm3 of water. What is the average density of the mixture?

A 6.0 m * 12.0 m swimming pool slopes linearly from a 1.0 m depth at one end to a 3.0 m depth at the other. What is the mass of water in the pool?

A 1.0-m-diameter vat of liquid is 2.0 m deep. The pressure at the bottom of the vat is 1.3 atm. What is the mass of the liquid in the vat?

The deepest point in the ocean is 11 km below sea level, deeper than Mt. Everest is tall. What is the pressure in atmospheres at this depth?

A 3.0-cm-diameter tube is held upright and filled to the top with mercury. The mercury pressure at the bottom of the tube the pressure in excess of atmospheric pressureis 50 kPa. How tall is the t

a. What volume of water has the same mass as 8.0 m3 of ethyl alcohol? b. If this volume of water is in a cubic tank, what is the pressure at the bottom?

A 50-cm-thick layer of oil floats on a 120-cm-thick layer of water. What is the pressure at the bottom of the water layer?

A research submarine has a 20-cm-diameter window 8.0 cm thick. The manufacturer says the window can withstand forces up to 1.0 * 106 N. What is the submarines maximum safe depth? The pressure inside the submarine is maintained at 1.0 atm.

A 20-cm-diameter circular cover is placed over a 10-cmdiameter hole that leads into an evacuated chamber. The pressure in the chamber is 20 kPa. How much force is required to pull the cover off?

The container shown in FIGURE EX14.12 is filled with oil. It is open to the atmosphere on the left. a. What is the pressure at point A? b. What is the pressure difference between points A and B? Between points A and C?

What is the height of a water barometer at atmospheric pressure?

What is the minimum hose diameter of an ideal vacuum cleaner that could lift a 10 kg (22 lb) dog off the floor?

How far must a 2.0-cm-diameter piston be pushed down into one cylinder of a hydraulic lift to raise an 8.0-cm-diameter piston by 20 cm?

A 6.00-cm-diameter sphere with a mass of 89.3 g is neutrally buoyant in a liquid. Identify the liquid

A 2.0 cm * 2.0 cm * 6.0 cm block floats in water with its long axis vertical. The length of the block above water is 2.0 cm. What is the blocks mass density?

Astronauts visiting a new planet find a lake filled with an unknown liquid. They have with them a plastic cube, 6.0 cm on each side, with a density of 840 kg/m3 . First they weigh the cube with a spring scale, measuring a weight of 21 N. Then they float the cube in the lake and find that two-thirds of the cube is submerged. At what depth in the lake will the pressure be twice the atmospheric pressure of 85 kPa?

A sphere completely submerged in water is tethered to the bottom with a string. The tension in the string is one-third the weight of the sphere. What is the density of the sphere?

A 5.0 kg rock whose density is 4800 kg/m3 is suspended by a string such that half of the rocks volume is under water. What is the tension in the string?

What is the tension of the string in FIGURE EX14.21?

A 10-cm-diameter, 20-cm-tall steel cylinder (rsteel = 7900 kg/m3 ) floats in mercury. The axis of the cylinder is perpendicular to the surface. What length of steel is above the surface?

You need to determine the density of a ceramic statue. If you suspend it from a spring scale, the scale reads 28.4 N. If you then lower the statue into a tub of water, so that it is completely submerged, the scale reads 17.0 N. What is the statues density?

Styrofoam has a density of 150 kg/m3 . What is the maximum mass that can hang without sinking from a 50-cm-diameter Styrofoam sphere in water? Assume the volume of the mass is negligible compared to that of the sphere

You and your friends are playing in the swimming pool with a 60-cm-diameter beach ball. How much force would be needed to push the ball completely under water?

Water flows through a 2.5-cm-diameter hose at 3.0 m/s. How long, in minutes, will it take to fill a 600 L childs wading pool?

A long horizontal tube has a square cross section with sides of width L. A fluid moves through the tube with speed v0. The tube then changes to a circular cross section with diameter L. What is the fluids speed in the circular part of the tube?

A 1.0-cm-diameter pipe widens to 2.0 cm, then narrows to 5.0 mm. Liquid flows through the first segment at a speed of 4.0 m/s. a. What is the speed in the second and third segments? b. What is the volume flow rate through the pipe?

A bucket is filled with water to a height of 23 cm, then a plug is removed from a 4.0-mm-diameter hole in the bottom of the bucket. As the water begins to pour out of the hole, how fast is it moving?

What does the top pressure gauge read in FIGURE EX14

A 2.0 mL syringe has an inner diameter of 6.0 mm, a needle inner diameter of 0.25 mm, and a plunger pad diameter (where you place your finger) of 1.2 cm. A nurse uses the syringe to inject medicine into a patient whose blood pressure is 140/100. a. What is the minimum force the nurse needs to apply to the syringe? b. The nurse empties the syringe in 2.0 s. What is the flow speed of the medicine through the needle?

A 70 kg mountain climber dangling in a crevasse stretches a 50-m-long, 1.0-cm-diameter rope by 8.0 cm. What is Youngs modulus for the rop

An 80-cm-long, 1.0-mm-diameter steel guitar string must be tightened to a tension of 2000 N by turning the tuning screws. By how much is the string stre

A 3.0-m-tall, 50-cm-diameter concrete column supports a 200,000 kg load. By how much is the column compressed?

a. What is the pressure at a depth of 5000 m in the ocean? b. What is the fractional volume change V/V of seawater at this pressure? c. What is the density of seawater at this pressure?

A large 10,000 L aquarium is supported by four wood posts (Douglas fir) at the corners. Each post has a square 4.0 cm * 4.0 cm cross section and is 80 cm tall. By how much is each post compressed by the weight of the aquarium?

A 5.0-m-diameter solid aluminum sphere is launched into space. By how much does its diameter increase? Give your answer in mm.

a. In FIGURE P14.38, how much force does the fluid exert on the end of the cylinder at A? b. How much force does the fluid exert on the end of the cylinder at B?

The two 60-cm-diameter cylinders in FIGURE P14.39, closed at one end, open at the other, are joined to form a single cylinder, then the air inside is removed. a. How much force does the atmosphere exert on the flat end of each cylinder? b. Suppose one cylinder is bolted to a sturdy ceiling. How many 100 kg football players would need to hang from the lower cylinder to pull the two cylinders apart?

Postural hypotension is the occurrence of low systolic blood pressure when a person stands up too quickly from a reclining position. A brain blood pressure lower than 90 mm of Hg can cause fainting or lightheadedness. In a healthy adult, the automatic constriction and expansion of blood vessels keep the brain blood pressure constant while posture is changing, but disease or aging can weaken this response. If the blood pressure in your brain is 118 mm of Hg while lying down, what would it be when you stand up if this automatic response failed? Assume your brain is 40 cm from your heart and the density of blood is 1060 kg/m3

A friend asks you how much pressure is in your car tires. You know that the tire manufacturer recommends 30 psi, but its been a while since youve checked. You cant find a tire gauge in the car, but you do find the owners manual and a ruler. Fortunately, youve just finished taking physics, so you tell your friend, I dont know, but I can figure it out. From the owners manual you find that the cars mass is 1500 kg. It seems reasonable to assume that each tire supports one-fourth of the weight. With the ruler you find that the tires are 15 cm wide and the flattened segment of the tire in contact with the road is 13 cm long. What answerin psiwill you give your friend?

a. The 70 kg student in FIGURE P14.42 balances a 1200 kg elephant on a hydraulic lift. What is the diameter of the piston the student is standing on? b. When a second student joins the first, the piston sinks 35 cm. What is the second students mass?

A 55 kg cheerleader uses an oil-filled hydraulic lift to hold four 110 kg football players at a height of 1.0 m. If her piston is 16 cm in diameter, what is the diameter of the football players piston?

A U-shaped tube, open to the air on both ends, contains mercury. Water is poured into the left arm until the water column is 10.0 cm deep. How far upward from its initial position does the mercury in the right arm rise?

Geologists place tiltmeters on the sides of volcanoes to measure the displacement of the surface as magma moves inside the volcano. Although most tiltmeters today are electronic, the traditional tiltmeter, used for decades, consisted of two or more water-filled metal cans placed some distance apart and connected by a hose. FIGURE P14.45 shows two such cans, each having a window to measure the water height. Suppose the cans are placed so that the water level in both is initially at the 5.0 cm mark. A week later, the water level in can 2 is at the 6.5 cm mark. a. Did can 2 move up or down relative to can 1? By what distance? b. Where is the water level now in can 1?

Glycerin is poured into an open U-shaped tube until the height in both sides is 20 cm. Ethyl alcohol is then poured into one arm until the height of the alcohol column is 20 cm. The two liquids do not mix. What is the difference in height between the top surface of the glycerin and the top surface of the alcohol?

An aquarium of length L, width (front to back) W, and depth D is filled to the top with liquid of density r. a. Find an expression for the force of the liquid on the bottom of the aquarium. b. Find an expression for the force of the liquid on the front window of the aquarium. c. Evaluate the forces for a 100-cm-long, 35-cm-wide, 40-cmdeep aquarium filled with water

Its possible to use the ideal-gas law to show that the density of the earths atmosphere decreases exponentially with height. That is, r = r0 exp(-z/z0), where z is the height above sea level, r0 is the density at sea level (you can use the Table 14.1 value), and z0 is called the scale height of the atmosphere. a. Determine the value of z0. Hint: What is the weight of a column of air? b. What is the density of the air in Denver, at an elevation of 1600 m? What percent of sea-level density is this?

The average density of the body of a fish is 1080 kg/m3 . To keep from sinking, a fish increases its volume by inflating an internal air bladder, known as a swim bladder, with air. By what percent must the fish increase its volume to be neutrally buoyant in fresh water? The density of air at 20C is 1.19 kg

A cylinder with cross-section area A floats with its long axis vertical in a liquid of density r. a. Pressing down on the cylinder pushes it deeper into the liquid. Find an expression for the force needed to push the cylinder distance x deeper into the liquid and hold it there. b. A 4.0-cm-diameter cylinder floats in water. How much work must be done to push the cylinder 10 cm deeper into the water?

A less-dense liquid of density r1 floats on top of a more-dense liquid of density r2. A uniform cylinder of length l and density r, with r1 6 r 6 r2, floats at the interface with its long axis vertical. What fraction of the length is in the more-dense liquid?

A 30-cm-tall, 4.0-cm-diameter plastic tube has a sealed bottom. 250 g of lead pellets are poured into the bottom of the tube, whose mass is 30 g, then the tube is lowered into a liquid. The tube floats with 5.0 cm extending above the surface. What is the density of the liquid?

One day when you come into physics lab you find several plastic hemispheres floating like boats in a tank of fresh water. Each lab group is challenged to determine the heaviest rock that can be placed in the bottom of a plastic boat without sinking it. You get one try. Sinking the boat gets you no points, and the maximum number of points goes to the group that can place the heaviest rock without sinking. You begin by measuring one of the hemispheres, finding that it has a mass of 21 g and a diameter of 8.0 cm. What is the mass of the heaviest rock that, in perfectly still water, wont sink the plastic boat?

A spring with spring constant 35 N/m is attached to the ceiling, and a 5.0-cm-diameter, 1.0 kg metal cylinder is attached to its lower end. The cylinder is held so that the spring is neither stretched nor compressed, then a tank of water is placed underneath with the surface of the water just touching the bottom of the cylinder. When released, the cylinder will oscillate a few times but, damped by the water, quickly reach an equilibrium position. When in equilibrium, what length of the cylinder is submerged?

A plastic boat with a 25 cm2 square cross section floats in a liquid. One by one, you place 50 g masses inside the boat and measure how far the boat extends below the surface. Your data are as follows: Mass added (g) Depth (cm) 50 2.9 100 5.0 150 6.6 200 8.6 Draw an appropriate graph of the data and, from the slope and intercept of the best-fit line, determine the mass of the boat and the density of the liquid.

A 355 mL soda can is 6.2 cm in diameter and has a mass of 20 g. Such a soda can half full of water is floating upright in water. What length of the can is above the water level?

A nuclear power plant draws 3.0 * 106 L/min of cooling water from the ocean. If the water is drawn in through two parallel, 3.0-m-diameter pipes, what is the water speed in each pipe?

a. A liquid of density r flows at speed v0 through a horizontal pipe that expands smoothly from diameter d0 to a larger diameter d1. The pressure in the narrower section is p0. Find an expression for the pressure p1 in the wider section. b. A pressure gauge reads 50 kPa as water flows at 10.0 m/s through a 16.8@cm@diameter horizontal pipe. What is the reading of a pressure gauge after the pipe has expanded to 20.0 cm in diameter?

A tree loses water to the air by the process of transpiration at the rate of 110 g/h. This water is replaced by the upward flow of sap through vessels in the trunk. If the trunk contains 2000 vessels, each 100 mm in diameter, what is the upward speed of the sap in each vessel? The density of tree sap is 1040 kg/m3

Water flows from the pipe shown in FIGURE P14.60 with a speed of 4.0 m/s. a. What is the water pressure as it exits into the air? b. What is the height h of the standing column of water?

The 1.0-m-tall cylinder in FIGURE P14.61 contains air at a pressure of 1 atm. A very thin, frictionless piston of negligible mass is placed at the top of the cylinder, to prevent any air from escaping, then mercury is slowly poured into the cylinder until no more can be added without the cylinder overflowing. What is the height h of the column of compressed air? Hint: Boyles law, which you learned in chemistry, says p1V1 = p2V2 for a gas compressed at constant temperature, which we will assume to be the case.

Water flowing out of a 16-mm-diameter faucet fills a 2.0 L bottle in 10 s. At what distance below the faucet has the water stream narrowed to 10 mm diameter?

Water from a vertical pipe emerges as a 10-cm-diameter cylinder and falls straight down 7.5 m into a bucket. The water exits the pipe with a speed of 2.0 m/s. What is the diameter of the column of water as it hits the bucket?

A 2.0-m-diameter vertical cylinder, open at the top, is filled with ethyl alcohol to the 2.5 m mark. A worker pulls a plug from a hole 55 cm from the bottom, causing the fluid level to begin dropping at a rate of 3.4 mm/min. What is the diameter of the hole?

A hurricane wind blows across a 6.0 m * 15.0 m flat roof at a speed of 130 km/h. a. Is the air pressure above the roof higher or lower than the pressure inside the house? Explain. b. What is the pressure difference? c. How much force is exerted on the roof? If the roof cannot withstand this much force, will it blow in or blow out?

Air flows through the tube shown in FIGURE P14.66 at a rate of 1200 cm3 /s. Assume that air is an ideal fluid. What is the height h of mercury in the right side of the U-tube?

Air flows through the tube shown in FIGURE P14.67. Assume that air is an ideal fluid. a. What are the air speeds v1 and v2 at points 1 and 2? b. What is the volume flow rate?

A water tank of height h has a small hole at height y. The water is replenished to keep h from changing. The water squirting from the hole has range x. The range approaches zero as y S 0 because the water squirts right onto the ground. The range also approaches zero as y S h because the horizontal velocity becomes zero. Thus there must be some height y between 0 and h for which the range is a maximum. a. Find an algebraic expression for the flow speed v with which the water exits the hole at height y. b. Find an algebraic expression for the range of a particle shot horizontally from height y with speed v. c. Combine your expressions from parts a and b. Then find the maximum range xmax and the height y of the hole. Real water wont achieve quite this range because of viscosity, but it will be close

a. A cylindrical tank of radius R, filled to the top with a liquid, has a small hole in the side, of radius r, at distance d below the surface. Find an expression for the volume flow rate through the hole. b. A 4.0-mm-diameter hole is 1.0 m below the surface of a 2.0-m-diameter tank of water. What is the rate, in mm/min, at which the water level will initially drop if the water is not replenished?

There is a disk of cartilage between each pair of vertebrae in your spine. Youngs modulus for cartilage is 1.0 * 106 N/m2 .Suppose a relaxed disk is 4.0 cm in diameter and 5.0 mm thick. If a disk in the lower spine supports half the weight of a 66 kg person, by how many mm does the disk compress?

The bottom of a steel boat is a 5.0 m * 10 m * 2.0 cm piece of steel (rsteel = 7900 kg/m3 ). The sides are made of 0.50-cmthick steel. What minimum height must the sides have for this boat to float in perfectly calm water?

The tank shown in FIGURE CP14.72 is completely filled with a liquid of density r. The right face is not permanently attached to the tank but, instead, is held against a rubber seal by the tension in a spring. To prevent leakage, the spring must both pull with sufficient strength and prevent a torque from pushing the bottom of the right face out. a. What minimum spring tension is needed? b. If the spring has the minimum tension, at what height d from the bottom must it be attached?

In FIGURE CP14.73, a cone of density ro and total height l floats in a liquid of density rf. The height of the cone above the liquid is h. What is the ratio h/l of the exposed height to the total height?

Disk brakes, such as those in your car, operate by using pressurized oil to push outward on a piston. The piston, in turn, presses brake pads against a spinning rotor or wheel, as seen in FIGURE CP14.74. Consider a 15 kg industrial grinding wheel, 26 cm in diameter, spinning at 900 rpm. The brake pads are actuated by 2.0-cmdiameter pistons, and they contact the wheel an average distance 12 cm from the axis. If the coefficient of kinetic friction between the brake pad and the wheel is 0.60, what oil pressure is needed to stop the wheel in 5.0 s

In addition to the buoyant force, an object moving in a liquid experiences a linear drag force F u drag = (bv, direction opposite the motion), where b is a constant. For a sphere of radius R, the drag constant can be shown to be b = 6phR, where h is the viscosity of the liquid. Consider a sphere of radius R and density r that is released from rest at the surface of a liquid with density rf. a. Find an expression in terms of R, h, g, and the densities for the spheres terminal speed vterm as it falls through the liquid. b. Solve Newtons second law to find an expression for vy1t2, the spheres vertical velocity as a function of time as it falls. Pay careful attention to signs! c. Water at 20C has viscosity h = 1.0 * 10-3 Pa s. Aluminum has density 2700 kg/m3 . If a 3.0-mm-diameter aluminum pellet is dropped into water, what is its terminal speed, and how long does it take to reach 90% of its terminal speed?

What are the overarching findings of Part III?

What laws of physics govern these applications?

What are the most important models of Part III?

What are the most important tools introduced in Part III?