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Straw Rocket Lab Research Materials

Rockets Research:

aeronautics: the study of the science of flight; the method of designing a flying machine

altitude: the distance upward a rocket travels

angle: the figure formed by two lines extending from the same point

apogee: the highest altitude a rocket reaches during flight

average: the mean value of a series of quantities, determined by dividing the sum by their number

constraint: limit

control: a standard by which experimental effectiveness is judged, unaffected by changed/tested variable

design: the process of creating diameter: the distance from one side of a circle to the other passing through the center of the circle

drag; the force that opposes an aircraft’s motion through the air, slowing it down

fin: a wing-like projection from the body of a rocket

force: a push or a pull on an object that causes it to undergo a change in speed, direction, or shape

gravity: a force of attraction between objects affected by mass of the objects and distance between them

lift: the force that directly opposes the weight of an airplane and hold it in the air

mass: the amount of matter within an object

modification: a change in the properties, form, or function

model rocket: a cylindrical projectile that can be propelled a distance

momentum: the product of mass and velocity

nose cone: the forward most, usually separable section of a rocket or guided missile that is shaped to offer minimum aerodynamic resistance and often bears protective cladding(cover) against heat

projectile: a fired, thrown, or otherwise propelled object

propulsion: the act of moving or pushing an object forward

range: the horizontal distance traveled during projectile motion

rocket: a self-propelled device that carries its own fuel

scatter plot: a two-dimensional graph of variables plotted to show relationships (best fit lines show average relationship)

thrust: the force that moves an aircraft through the

air; used to overcome the drag of an airplane or the

weight of a rocket

trajectory: the curve described by a projectile in

flight

variable: subject to change; a quantity that may

assume any set of values

velocity: speed and direction of an object’s motion

weight: amount of force that gravity exerts on an

object’s mass

Careers Related to Aerospace Design and

Engineering

aerodynamicist- aircraft manufacturing

aerospace project engineer

drafter, aeronautical

flight-test data acquisition technician

machinist

mechanical engineer

target aircraft technician- military Additional information about each career can be found by logging on to http://www.occupationalinfo.org/

Cannell, Tim. Straw Rockets: STEM Curriculum. Pittsburg, KS: Pitsco Education, 2011. R-79,92. Print.


How Rockets Work

Dunbar, Brian, ed. "How Rockets Work." Adventures in Celestial Mechanics (2011): 65-84. NASA: Rockets

Educator Guide. NASA, 1 July 2016. Web. 21 Oct. 2016.

Whether flying a small model rocket or launching a giant cargo rocket to Mars, the principles of how rockets

work are exactly the same. Understanding and applying these principles means mission success. In the early

days of rocketry, the flight of a fire arrow or other rocket device was largely a matter of chance. It might fly; it

might skitter about, shooting sparks and smoke; or it might explode. Through centuries of trial and error,

rockets became more reliable. However, real advancements in rocketry depended upon a scientific and

mathematical understanding of motion. That came in the seventeenth century with the works of scientists such

as Galileo and Isaac Newton.

Galileo conducted a wide range of experiments involving motion. Through studies of inclined planes, Galileo

concluded that moving objects did not need the continuous application of force (in the absence of friction and

drag) to keep moving. Galileo discovered the principle of inertia, that all matter, because of its mass, resists

changes in motion. The more mass, the more resistance there is. Isaac Newton, born the year Galileo died,

advanced Galileo’s discoveries and those of others by proposing three basic laws of motion. These laws are the

foundation of all rocket science. Understand the laws and

you know just about everything you need to build

successful rockets. Apply the laws and you become a

“rocket scientist.”

Newton’s Laws of Motion

In his master work entitled Philosophia Naturalis

Principia Mathematica (usually referred to as Principia),

Isaac Newton stated his laws of motion. For the most

part, the laws were known intuitively by rocketeers, but

their statement in clear form elevated rocketry to a

science. Practical application of Newton’s laws makes the

difference between failure and success. The laws relate

force and direction to all forms of motion.

Before looking at each of these laws in detail, a few terms should be explained.

Rest and Motion, as they are used in the first law, can be confusing. Both terms are relative. They mean rest or

motion in relation to surroundings. You are at rest when sitting in a chair. It doesn’t matter if the chair is in the

cabin of a jet plane on a cross-country flight. You are still considered to be at rest because the airplane cabin is

moving along with you. If you get up from your seat on the airplane and walk down the aisle, you are in relative

motion because you are changing your position inside the cabin.

Force is a push or a pull exerted on an object. Force can be exerted in many ways, such as muscle power,

movement of air, and electromagnetism, to name a few. In the case of rockets, force is usually exerted by burning

rocket propellants that expand explosively. Unbalanced Force refers to the sum total or net force exerted on an


object. The forces on a coffee cup sitting on a desk, for example, are in balance. Gravity is exerting a downward

force on the cup. At the same time, the structure of the desk exerts an upward force, preventing the cup from

falling. The two forces are in balance.

Reach over and pick up the cup. In doing so, you unbalance

the forces on the cup. The weight you feel is the force of gravity

acting on the mass of the cup. To move the cup upward, you

have to exert a force greater than the force of gravity. If you

hold the cup steady, the force of gravity and the muscle force

you are exerting are in balance.

Unbalanced force also refers to other motions. The forces on

a soccer ball at rest on the playing field are balanced. Give the

ball a good kick, and the forces become unbalanced. Gradually,

air drag (a force) slows the ball, and gravity causes it to bounce

on the field. When the ball stops bouncing and rolling, the

forces are in balance again.

Take the soccer ball into deep space, far away from any star

or other significant gravitational field, and give it a kick. The

kick is an unbalanced force exerted on the ball that gets it

moving. Once the ball is no longer in contact with the foot, the

forces on the ball become balanced again, and the ball will travel in a straight line forever.

How can you tell if forces are balanced or unbalanced? If the

soccer ball is at rest, the forces are balanced. If the ball is moving

at a constant speed and in a straight line, the forces are balanced.

If the ball is accelerating or changing its direction, the forces are

unbalanced.

Mass is the

amount of matter

contained in an

object. The object

does not have to

be solid. It could

be the amount of

air contained in a

balloon or the

amount of water

in a glass. The

important thing about mass is that unless you alter it in some

way, it remains the same whether the object is on Earth, in Earth

orbit, or on the Moon. Mass just refers to the quantity of matter contained in the object. (Mass and weight are


often confused. They are not the same thing. Weight is a force and is the product of mass times the acceleration

of gravity.)

Acceleration relates to motion. It means a change in motion. Usually, change refers to increasing speed, like

what occurs when you step on the accelerator pedal of a car. Acceleration also means changing direction.

This is what happens on a carousel. Even though the carousel is turning at a constant rate, the continual change

in direction of the horses and riders (circular motion) is acceleration.

Action is the result of a force. A cannon fires, and the cannon ball flies through the air. The movement of the

cannon ball is an action. Release air from an inflated balloon. The air shoots out the nozzle. That is also an action.

Step off a boat onto a pier. That, too, is an action.

Reaction is related to action. When the cannon fires, and the cannon ball flies through the air, the cannon itself

recoils backward. That is a reaction. When the air rushes out of the balloon, the balloon shoots the other way,

another reaction. Stepping off a boat onto to a pier causes a reaction. Unless the boat is held in some way, it

moves in the opposite direction. (Note: The boat example is a great demonstration of the action/reaction

principle, providing you are not the one stepping off the boat!)

Newton’s First Law

This law is sometimes referred to as Galileo’s law of inertia because Galileo discovered the principle of inertia.

This law simply points out that an object at rest, such as a rocket on a launch pad, needs the exertion of an

unbalanced force to cause it to lift off. The amount of the thrust (force) produced by the rocket engines has to be

greater than the force of gravity holding it down. As long as the thrust of the engines continues, the rocket

accelerates. When the rocket runs out of propellant, the forces become unbalanced again. This time, gravity takes

over and causes the rocket to fall back to Earth. Following its “landing,” the rocket is at rest again, and the forces

are in balance.

There is one very interesting part of this law that has enormous implications for spaceflight. When a rocket

reaches space, atmospheric drag (friction) is greatly reduced or eliminated. Within the atmosphere, drag is an

important unbalancing force. That force is virtually absent in space. A rocket traveling away from Earth at a speed

greater than 11.186 kilometers per second (6.95 miles per second) or 40,270 kilometers per hour (25,023 mph)

will eventually escape Earth’s gravity. It will slow down, but Earth’s gravity will never slow it down enough to

cause it to fall back to Earth. Ultimately, the rocket (actually its payload) will travel to the stars. No additional

rocket thrust will be needed. Its inertia will cause it to continue to travel outward. Four spacecraft are actually

doing that as you read this. Pioneers 10 and 11 and Voyagers 1 and 2 are on journeys to the stars!


Newton’s Third Law

(It is useful to jump to the third law and come back to the second law later.) This is

the law of motion with which many people are familiar. It is the principle of action

and reaction. In the case of rockets, the action is the force produced by the expulsion

of gas, smoke, and flames from the nozzle end of a rocket engine. The reaction force

propels the rocket in the opposite direction.

When a rocket lifts off, the combustion products from the burning propellants

accelerate rapidly out of the engine. The rocket, on the other hand, slowly accelerates

skyward. It would appear that something is wrong here if the action and reaction are

supposed to be equal. They are equal, but the mass of the gas, smoke, and flames

being propelled by the engine is much less than the mass of the rocket being propelled

in the opposite direction. Even though the force is equal on both, the effects are

different.

Newton’s first law, the law of inertia, explains why. The law states that it takes a force

to change the motion of an object. The greater the mass, the greater the force

required to move it.

Newton’s Second Law

The second law relates force, acceleration, and mass. The law is often written as

the equation: f = ma

The force or thrust produced by a rocket engine is directly proportional to the mass

of the gas and particles produced by burning rocket propellant times the acceleration of those combustion

products out the back of the engine. This law only applies to what is actually traveling out of the engine at the

moment and not the mass of the rocket propellant contained in the rocket that will be consumed later.

The implication of this law for rocketry is that the more propellant (m) you consume at any moment and the

greater the acceleration (a) of the combustion products out of the nozzle, the greater the thrust (f).

A Taste of Real Rocket Science

Naturally, launching rockets into space is more complicated than Newton’s laws of motion imply. Designing

rockets that can actually lift off Earth and reach orbital velocities or interplanetary space is an extremely

complicated process. Newton’s laws are the beginning, but many other things come into play. For example, air

pressure plays an important role while the rocket is still in the atmosphere. The internal pressure produced by

burning rocket propellants inside the rocket engine combustion chamber has to be greater than the outside

pressure to escape through the engine nozzle. In a sense, the outside air is like a cork in the engine. It takes some

of the pressure generated inside the engine just to exceed the ambient outside pressure. Consequently, the

velocity of combustion products passing through the opening or throat of the nozzle is reduced. The good news

is that as the rocket climbs into space, the ambient pressure becomes less and less as the atmosphere thins and

the engine thrust increases.

Another important factor is the changing mass of the rocket. As the rocket is gaining thrust as it accelerates

upward due to outside pressure changes, it is also getting a boost due to its changing mass. Every bit of rocket


propellant burned has mass. As the combustion products are ejected by the engine, the total mass of the vehicle

lessens. As it does its inertia, or resistance to change in motion, becomes less. As a result, upward acceleration

of the rocket increases.

In practical terms, Newton’s second law can be

rewritten as this:

f = mexitVexit + (pexit - pambient)Aexit

(“A” refers to the area of the engine throat.)

When the rocket reaches space, and the exit pressure minus the ambient pressure becomes zero, the equation

becomes:

f = mexitVexit

In real rocket science, many other things also come into play.

• Even with a low acceleration, the rocket will gain speed over time because acceleration accumulates.

• Not all rocket propellants are alike. Some produce much greater thrust than others because of their burning

rate and mass. It would seem obvious that rocket scientists would always choose the more energetic propellants.

Not so. Each choice a rocket scientist makes comes with a cost. Liquid hydrogen and liquid oxygen are very

energetic when burned, but they both have to be kept chilled to very low temperatures. Furthermore, their mass

is low, and very big tanks are needed to contain enough propellant to do the job.

In Conclusion...

Newton’s laws of motion explain just about everything you need to know to become a rocket scientist.

However, knowing the laws is not enough. You have to know how to apply them, such as:

- How can you create enough thrust to exceed the weight of the rocket?

- What structural materials and propellant combinations should you use?

- How big will the rocket have to be?

- How can you make the rocket go where you want it to?

- How can you bring it back to Earth safely?


Modeling Clay Research:

McMahon, Mary, and Kristen Osborne. "What Is Modeling Clay." WiseGeek. Conjecture, 2008.

Web. 21 Oct. 2016.

Modeling clay is a flexible material that can be molded in a variety of ways and may be very long-lasting, in the case of hardening clays. A number of materials can be used to make modeling clay and some products do not actually contain true clays, but are workable and behave like clay. These products are used by crafters, artists, and technical designers who may have reason to make clay models. They are also used in a type of animation known as claymation.

Ceramic, oil, dough, paper, and polymers can all be used as a base for modeling clay. The most appropriate type of modeling clay to use can depend on the application. Broadly, they are divided into hardening and non-hardening clays. Non-hardening clays like those used in claymation remain flexible so they can be adjusted. Hardening clays are designed to firm up to make a permanent project.

Some hardening clays air harden and will dry simply by being left out. If the user still wants to work on a project, she can mist it with liquid and bag it in plastic to prevent water loss. Other clays harden when exposed to heat, either in an oven for home crafts or a kiln. In the case of pottery clays, the clay undergoes a chemical transformation in the kiln and will change structure to create a very hard finished product.

Paper clays tend to be fast drying and lightweight. Polymer clays can be flexible or hardening and may be useful for a wide range of projects, while pottery clays are typically heavy. Dough clays are common for home crafts, especially with children who want to explore modeling. Some are nontoxic and designed specifically for kids. They also take dyes very well and can be blended to create different shades and tints of color.

Revolvy, LLC. "Modelling Clay" 1 Jan. 2014. Web. 21 Oct. 2016.

Oil-based clay Oil-based clays are made from various combinations of oils, waxes, and clay minerals. Because the oils do not evaporate like water, oil-based clays remain malleable even when left in dry environments for long periods. Articles made from oil-based clays cannot be fired, and thus are not ceramics. Because rising temperature decreases oil viscosity, the malleability is influenced by heating or cooling the clay. Oil-based clay is not water-soluble. As it can be re-used, it is a popular material for animation artists who need to bend and move their models. It is available in a multitude of colors and is non-toxic. Oil-based clays are referred to by a number of generalized trademarks. Plastilin, which was patented in Germany by Franz Kolb in 1880, was developed by Claude Chavant in 1892 and trademarked in 1927. Plasticine was invented in 1897 by William Harbutt of Bathampton, England. Plastilina is trademarked as Roma Plastilina by Sculpture House, Inc. According to their website, their formula is 100 years old. Roma Plastilina contains sulfur, and since certain mold-making compounds do not set in sulfur's presence, making molds of items made of industrial plasticine is difficult. In India, oil-based "No Sulphur" clay is manufactured by Uday Industries for industrial, as well as retail use. Readily worked in fine detail, oil-based clays are also suitable for the creation of detailed sculptures from which molds can be made. Castings and reproductions can then be produced from much more durable materials. Cars and airplanes may be created using industrial design-grade modelling clay.


How Products Are Made "Drinking Straw." How Drinking Straw Is Made. Advameg, Inc. Web. 21 Oct. 2016.

Drinking Straw

Background

A straw is a prepared tube used to suck a beverage out of a container. Historians theorize

the first straws were cut from dried wheat shafts and they were named accordingly. With the

advent of industrial age, methods were developed to mass produce straws by rolling

elongated sheets of wax-coated paper into a cylindrical, hollow tubes. This was

accomplished by coiling paraffin-coated paper around a rod-shaped form and then securing

the paper with an adhesive. The entire straw was then coated with wax to further water-

proof it. The wax coating was important since the straw was paper and would eventually

absorb some of the liquid being sucked up it. Thus, inevitably these paper straws became

soggy and useless. In the 1960s, paper was largely replaced by plastic which were becoming

less expensive and increasingly more sophisticated. The explosion of plastic technology led

to techniques to manufacture plastic straws via extrusion. Today, straws are made in a wide

variety of shapes, colors, and functions.

Raw Materials

Straws are made from a formulated blend of plastic resin, colorants, and other additives.

Plastic

Historically, straws have been made from paper but today polypropylene plastic is the

material of choice. Polypropylene is a resin made by polymerizing, or stringing together,

molecules of a propylene gas. When a very large number of these molecules are chemically

hooked together they form this solid plastic material. Polypropylene was first developed in

the mid-1950s and has many properties, which make it suitable for use in straw

manufacturing. This resin is light-weight, has fair abrasion resistance, good dimensional

stability, and good surface hardness. It typically does not experience problems with stress

cracking and it offers excellent chemical resistance at higher temperatures. Most importantly

for this application, it has good thermoplastic properties. This means it can be melted,

formed into various shapes and, upon reheating, can be melted and molded again. Another

key attribute of this plastic is that it is safe for contact with food and beverage.


Polypropylene is approved for indirect contact with food and, in addition to drinking straws,

is used to make many types of food packaging such as margarine and yogurt containers,

cellophane-type wrapping, and various bottles and caps.

Colorants

Colorants can be added to the plastic to give the straws an aesthetically pleasing

appearance. However, in the United States, the colorants used must be chosen from a list of

pigments approved by the Food and Drug Administration (FDA) for food contact. If the

colorants are not food grade, they must be tested to make sure they will not leach out of

the plastic and into the food or beverage. These pigments are typically supplied in

powdered form, and a very small amount is required to impart bright colors. Through use of

multiple colorants, multi-colored straws can be made.

Other additives

Additional materials are added to the plastic formula to control the physical properties of

the finished straw. Plasticizers (materials which improve the flexibility of the polypropylene)

may be added to keep the resin from cracking. Antioxidants are used to reduce harmful

interactions between the plastic and the oxygen in the air. Other stabilizers

include ultraviolet light filters, which shield the plastic from the effects of sunlight and

prevent the radiation from adversely effecting the plastic. Finally, inert fillers may be added

to increase the bulk density of the plastic. All these materials must meet appropriate FDA

requirements.

Packaging materials

Straws are typically wrapped in paper sleeves for individual use or bulk packed in plastic

pouches or cardboard boxes.

The Manufacturing

Process

Straw manufacturing requires several steps. First, the plastic resin and other components are

mixed together; the mixture is then extruded in a tube shape; the straw may under go

subsequent specialized operations; and finally the straws are packaged for shipment.

Plastic compounding


1 The polypropylene resin must first be mixed with the plasticizers, colorants, antioxidants,

stabilizers, and fillers. These materials, in powder form, are dumped into the hopper of an

extrusion compounder that mixes, melts, and forms beads of the blended plastic. This

machine can be thought of as a long, heated, motor driven meat grinder. The powders are

mixed together and melted as they travel down the barrel of the extruder. Special feeder

screws are used to push the powder along its path. The molten plastic mixture is squeezed

out through a series of small holes at the other end of the extruder. The holes shape the

plastic into thin strands about 0.125 inch (0.3175 cm) in diameter. One compounding method

ejects these strands into cooling water where a series of rotating knives cut them into short

pellets. The pellet shape is preferred for subsequent molding operations because pellets are

easier to move than a fine powder. These pellets are then collected and dried; they may be

further blended or coated with other additives before packaging. The finished plastic pellets

are stored until they are ready to be molded into straws.

Straw extrusion

2 The pellets are transferred to another extrusion molder. The second extruder is fitted with a

different type of die, which produces a hollow tube shape. The pellets are dumped in a

hopper on one end of the machine and are forced through a long channel by a screw

mechanism. This screw is turned in the barrel with power supplied by a motor operating

through a gear reducer. As the screw rotates, it moves the resin down the barrel. As the resin

travels down the heated channel, it melts and becomes more flowable. To ensure good

movement and heat transfer, the screw fits within the barrel with only few thousands of an

inch clearance. It is machined from a solid steel rod, and the surfaces almost touching the

barrel are hardened to resist wear. By the time the resin reaches the end of the barrel, it is

completely melted and can be easily forced out through the opening in the die.

3 The resin exits the die in a long string in the shape of a straw. It is then moved along by a

piece of equipment known as a puller which helps maintain the shape of the straw as it is

moved through the rest of the manufacturing process. In some processes, it is necessary to

pull the straw through special sizing plates to better control the diameter. These plates are

essentially metal sheets with holes drilled in them. Eventually, this elongated tube is directed

through a cooling stage—usually a water bath. Some operations run the plastic over a chilled

metal rod, called a mandrel, which freezes the internal dimension of the straw to that of the

rod. Ultimately, the long tubes are cut to the proper length by a knife assembly.

Special operations


4 Straws with special design requirements may undergo additional processing. For example,

so called "crazy" straws, which have a series of loops and turns, may be bent into shape using

special molding equipment. Another type of straw with special manufacturing requirements is

the "bendable" straw. This type of straw can bend in the middle and is made using a special

device that creates

Plastic drinking straws are extruded through an injection molding machine.

a series of grooves that allow the straw to flex. These grooves can be crimped into the straws

in a two step process. First, it is first necessary to "pick up" the straw so it can be

manipulated. This can be accomplished by spreading the straws across a flat plate, which has

slots cut in it. The straws will tend to roll into the slots and remain there. The slots are evenly

spaced and are adjacent to a separate metal plate, which has a series of metal pins extending

from it. The pins are aligned in a parallel fashion with the slots on the plate. Once the straws

have come to rest in the slots, the pins can be easily inserted into the straws. The straws can

then be easily lifted up and moved around in any orientation by simply manipulating the

plate that holds the pins. The steel pins holding the straws have a series of parallel rings cut

into them. As the straws are wrapped around the pin, they are gripped by a pair of semi-

circular steel jaws, which have a complementary set of rings. The jaws crimp a series of rings

into the straw. The crimp pattern allows the straws to bend without closing off. After these

operations, the straws can then by proceed to packaging.


Quality Control

Drinking straw quality is determined at a number of key steps during the compounding and

extrusion phases of the manufacturing process as well as after extrusion is complete. During

compounding, the mixing process must be monitored to ensure the formula components

are blended in the proper ratios. Before beginning the extrusion process, it is a common

practice to purge some resin through the extruder. This purging helps clean out the barrel

and acts as a check to make sure all molding systems are operating properly. At this stage,

sample straws can be checked to make sure they achieve the proper dimensions. These

samples can also be used to ensure manufacturing equipment is operating at the proper

line speed.

During the extrusion process, it is critical that the resin is be kept at the proper temperature.

Depending on the processing temperature (and the molecular weight of the polymer),

plastic can flow as slowly as tar or as quickly as corn syrup. If the temperature is too cool,

the viscosity increases dramatically, and the resin will not flow through the die. If the

temperature is too high, thermal breakdown can occur. Over-heating can cause chemical

changes in the resin, weakening the plastic and rendering it unsuitable for use in straw

manufacturing. Under certain circumstances, die buildup occurs. When this happens, a glob

of plastic gets stuck somewhere in the die. This glob eventually breaks free, becomes

attached to the molded straw, and ruins its appearance. Unwanted chemical interactions can

also effect the quality of the finished straws during the extrusion process. One problem is

oxidation, which results from contact with air. This reaction can negatively impact the plastic.

Similarly, the plastic interacts with any moisture that is present; too little moisture can make

certain plastic blends too brittle.

After the manufacturing process is complete, it is critical that the extruder be properly

cleaned. Thorough cleaning is necessary because different types of different colored plastics

can be left behind in the extruder barrel. This residue can cause contamination in the next

batch that is made. Die cleaning is done when the machine is still hot and traces of resin

can be easily scraped from the metal.

Byproducts/Waste

The major waste product from straw manufacturing is the plastic resin. Resin, which is

contaminated, overheated, or otherwise ruined must be discarded. However, straws, which


fail for other reasons, can be reworked. This process of reusing plastic is known as

regrinding and involves pulverizing the straws and remelting them. This can be done

without loss of quality because of the thermoplastic nature of polypropylene.

The Future

There are a number of interesting new developments in straw technology. First, new and

improved plastic blends are constantly being evaluated. This is necessary to keep costs

down, meet regulatory requirements, and improve quality. In addition, new processing and

design methods are being developed. These can expand the straws into new areas. For

example, thermoliquid crystals, a special colorant that responds to changes in temperature,

can be added to straws to make them change color when they come in contact with hot or

cold liquid. Other unique applications include ways of printing straws with the identity of the

beverage (e.g., diet, root beer, etc.). The straw can then be used to mark what the drink

contains. Other advances include straws made by a blow molding process, which creates

faces or other artifacts in the middle of the straw.

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