Equipment and Supplies
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Wikipedia-Article "Equipment"
- For other uses, see Tool (disambiguation).
A tool is a device that provides a mechanical or mental advantage in accomplishing a simple machine, or a combination of them. For example, a crowbar simply functions as a lever. The further out from the pivot point, the more force is transmitted along the lever.
Philosophers once thought that only humans used tools, and often defined humans as tool-using animals. But observation has confirmed that monkeys and other animals, mostly primates, but also some birds (ravens, for instance), and sea otters can use tools as well. Later, philosophers thought that only humans had the ability to make tools, until zoologists observed birds[1] and monkeys[2][3][4] making tools. Most anthropologists believe that the use of tools was an important step in the evolution of mankind. Humans evolved an opposable thumb (useful to hold the tools) and an increase in intelligence (aiding in the use of tools).
Most tools can also serve as weapons, such as the hammer and the knife. Similarly, people can use weapons, such as explosives, as tools.
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Varieties of tools
- Devices often typify newly invented or specific-purpose tools.
- Instruments are concrete or abstract tools, especially if they are refined.
- Utensils aid in eating.
- Machines can function as ordered systems of tools or as super-tools.
Physical tools
- Hand tools such as pliers, adze, or axe
- Agricultural tools such as scythe or sickle
- Power tools such as drill or wood router
- Machine tools such as lathe, milling machine or shaping machine
- Hydraulic tools such as the Hurst tool or hydraulic ram
- Heat-based tools such as soldering iron, welding torch and thermic lance
- Eating utensils such as chopsticks, fork, knife, or spoon
- Writing instruments such as ballpoint pen or pencil
- Special use tools such as Buggy whip or whetstone
- Multitools such as Swiss Army knife or Leatherman
Toy tools make popular playthings. Some simply consist of a cheap or small version of the real thing, such as a shovel and bucket to use on the beach or in a sandbox. Others are less functional, e.g. a dull plastic knife, or not functional at all.
Mental tools
- Language
- Logic
- Tradition
- Algorithms
- Memorization, such as being mindful that physical tools may be recalled from a list
In computing, the term \"tools\" can also apply to software programs that assist people doing work on computers, such as Computer Aided Software Engineering tools, Lint programming tool, software or web-based collaborative tools, software development tools, programming tools.
Slang Usage
Stemming from a double-entendre where a "tool" is a phallus; this became a popular word in the 1990's. Individuals may be described as "tools", as an insult meaning that someone is a klutz or easily taken advantage of.
Functions of tools
Many tools or groups of tools serve to perform one or more of a set of basic operations, such as:
- Cutting (knife, scythe, sickle, ...)
- Concentrating force (hammer, maul, screwdriver, whip, writing implements, ...)
- Guiding (set square, algorithm, straight edge, tradition, ...)
- Protecting
- Seizing and holding (pliers, glove, wrench, ...)
History
Use of tools started at the beginning of the Stone age. Humans have fabricated knives, amongst the oldest tools, since that time.
Mechanical devices, though known to Alexandrian Greeks, experienced a major expansion in their use in the Middle Ages with the systematic employment of new energy sources: water (waterwheels) and wind (windmills).
Machine tools occasioned a surge in producing new tools in the Industrial revolution. Advocates of nanotechnology expect a similar surge as tools move down-scale.
WikiProject Metalworking: This article is part of Metalworking hand tools.
Wikipedia-Article "Supplies"
In microeconomic theory, the partial equilibrium supply and demand economic model originally developed by Alfred Marshall attempts to describe, explain, and predict changes in the price and quantity of goods sold in competitive markets. The model is only a first approximation for describing an imperfectly competitive market. It formalizes the theories used by some economists before Marshall and is one of the most fundamental models of some modern economic schools, widely used as a basic building block in a wide range of more detailed economic models and theories. The theory of supply and demand is important for some economic schools' understanding of a market economy in that it is an explanation of the mechanism by which many resource allocation decisions are made. However, unlike general equilibrium models, supply schedules in this partial equilibrium model are fixed by unexplained forces.
Demand
Demand is that quantity of a good that consumers are not only willing to purchase but also have the capacity to buy at the given price. For example, a consumer may be willing to purchase 2 lb of potatoes if the price is $0.75 per lb. However, the same consumer may be willing to purchase only 1 lb if the price is $1.00 per lb. A demand schedule can be constructed that shows the quantity demanded at each given price. It can be represented on a graph as a line or curve by plotting the quantity demanded at each price. It can also be described mathematically by a demand equation. The main determinants of the quantity one is willing to purchase will typically be the price of the good, one's level of income, personal tastes, the price of substitute goods, and the price of complementary goods.
The shape of the aggregated demand curve can be convex or concave, possibly depending on income distribution, as shown in this paper: http://www.economicswebinstitute.org/essays/consumers.htm
Supply
Supply is the quantity that producers are willing to sell at a given price. For example, the potato grower may be willing to sell 1 million lb of potatoes if the price is $0.75 per lb and substantially more if the market price is $0.90 per lb. The main determinants of supply will be the market price of the good and the cost of producing it. In fact, supply curves are constructed from the firm's long-run cost schedule.
Simple supply and demand curves
Mainstream economic theory centers on creating a series of supply and demand relationships, describing them as equations, and then adjusting for factors which produce "stickiness" between supply and demand. Analysis is then done to see what "trade offs" are made in the "market", which is the negotiation between sellers and buyers. Analysis is done as to what point the ability of sellers to sell becomes less useful than other opportunities. This is related to "marginal" costs, or the price to produce the last unit that can be sold profitably, versus the chance of using the same effort to engage in some other activity.
The slope of the demand curve (downward to the right) indicates that a greater quantity will be demanded when the price is lower. On the other hand, the slope of the supply curve (upward to the right) tells us that as the price goes up, producers are willing to produce more goods. The point where these curves intersect is the equilibrium point. At a price of P producers will be willing to supply Q units per period of time and buyers will demand the same quantity. P in this example, is the equilibrating price that equates supply with demand.
In the figures, straight lines are drawn instead of the more general curves. This is typical in analysis looking at the simplified relationships between supply and demand because the shape of the curve does not change the general relationships and lessons of the supply and demand theory. The shape of the curves far away from the equilibrium point are less likely to be important because they do not affect the market clearing price and will not affect it unless large shifts in the supply or demand occur. So straight lines for supply and demand with the proper slope will convey most of the information the model can offer. In any case, the exact shape of the curve is not easy to determine for a given market. The general shape of the curve, especially its slope near the equilibrium point, does however have an impact on how a market will adjust to changes in demand or supply. (See the below section on elasticity.)
It should be noted that on supply and demand curves both are drawn as a function of price. Neither is represented as a function of the other. Rather the two functions interact in a manner that is representative of market outcomes. The curves also imply a somewhat neutral means of measuring price. In practice any currency or commodity used to measure price is also the subject of supply and demand.
Effects of being away from the equilibrium point
Consider how prices and quantities not at the equilibrium point tend to move towards the equilibrium. Assume that some organization (say government or industry cartel) has the ability to set prices. If the price is set too high, such as at P1 in the diagram to the right, then the quantity produced will be Qs. The quantity demanded will be Qd. Since the quantity demanded is less than the quantity supplied there will be an oversupply (also called surplus or excess supply). On the other hand, if the price is set too low, then too little will be produced to meet demand at that price. This will cause an undersupply problem (also called a shortage).
Now assume that individual firms have the ability to alter the quantities supplied and the price they are willing to accept, and consumers have the ability to alter the quantities that they demand and the amount they are willing to pay. Businesses and consumers will respond by adjusting their price (and quantity) levels and this will eventually restore the quantity and the price to the equilibrium.
In the case of too high a price and oversupply (seen in the diagram at the left), the profit-maximizing businesses will soon have too much excess inventory, so they will lower prices (from P1 to P) to reduce this. Quantity supplied will be reduced from Qs to Q and the oversupply will be eliminated. In the case of too low a price and undersupply, consumers will likely compete to obtain the good at the low price, but since more consumers would like to buy the good at the price that is too low, the profit-maximizing firm would raise the price to the highest they can, which is the equilibrium point. In each case, the actions of independent market participants cause the quantity and price to move towards the equilibrium point.
Demand curve shifts
When more people want something, the quantity demanded at all prices will tend to increase. This can be referred to as an increase in demand. The increase in demand could also come from changing tastes, where the same consumers desire more of the same good than they previously did. Increased demand can be represented on the graph as the curve being shifted right, because at each price point, a greater quantity is demanded. An example of this would be more people suddenly wanting more coffee. This will cause the demand curve to shift from the initial curve D0 to the new curve D1. This raises the equilibrium price from P0 to the higher P1. This raises the equilibrium quantity from Q0 to the higher Q1. In this situation, we say that there has been an increase in demand which has caused an extension in supply.
Conversely, if the demand decreases, the opposite happens. If the demand starts at D1 and then decreases to D0, the price will decrease and the quantity supplied will decrease—a contraction in supply. Notice that this is purely an effect of demand changing. The quantity supplied at each price is the same as before the demand shift (at both Q0 and Q1). The reason that the equilibrium quantity and price are different is the demand is different.
Supply curve shifts
When the suppliers' costs change the supply curve will shift. For example, assume that someone invents a better way of growing wheat so that the amount of wheat that can be grown for a given cost will increase. Producers will be willing to supply more wheat at every price and this shifts the supply curve S0 to the right, to S1—an increase in supply. This causes the equilibrium price to decrease from P0 to P1. The equilibrium quantity increases from Q0 to Q1 as the quantity demanded increases at the new lower prices. Notice that in the case of a supply curve shift, the price and the quantity move in opposite directions.
Conversely, if the quantity supplied decreases, the opposite happens. If the supply curve starts at S1 and then shifts to S0, the equilibrium price will increase and the quantity will decrease. Notice that this is purely an effect of supply changing. The quantity demanded at each price is the same as before the supply shift (at both Q0 and Q1). The reason that the equilibrium quantity and price are different is the supply is different.
See also: Induced demand
Market "clearance"
The market "clears" at the point where all the supply and demand at a given price balance. That is, the amount of a commodity available at a given price equals the amount that buyers are willing to purchase at that price. It is assumed that there is a process that will result in the market reaching this point, but exactly what the process is in a real situation is an ongoing subject of research. Markets which do not clear will react in some way, either by a change in price, or in the amount produced, or in the amount demanded. Graphically the situation can be represented by two curves: one showing the price-quantity combinations buyers will pay for, or the demand curve; and one showing the combinations sellers will sell for, or the supply curve. The market clears where the two are in equilibrium, that is, where the curves intersect. In a general equilibrium model, all markets in all goods clear simultaneously and the "price" can be described entirely in terms of tradeoffs with other goods. For a century most economists believed in Say's Law, which states that markets, as a whole, would always clear and thus be in balance.
Elasticity
Main article: Elasticity (economics)
An important concept in understanding supply and demand theory is elasticity. In this context, it refers to how supply and demand change in response to various stimuli. One way of defining elasticity is the percentage change in one variable divided by the percentage change in another variable (known as arch elasticity because it calculates the elasticity over a range of values, in contrast with point elasticity that uses differential calculus to determine the elasticity at a specific point). Thus it is a measure of relative changes.
Often, it is useful to know how the quantity supplied or demanded will change when the price changes. This is known as the price elasticity of demand and the price elasticity of supply. If a monopolist decides to increase the price of their product, how will this affect their sales revenue? Will the increased unit price offset the likely decrease in sales volume? If a government imposes a tax on a good, thereby increasing the effective price, how will this affect the quantity demanded?
If you do not wish to calculate elasticity, a simpler technique is to look at the slope of the curve. Unfortunately, this has units of measurement of quantity over monetary unit (for example, liters per euro, or battleships per million yen), which is not a convenient measure to use for most purposes. So, for example, if you wanted to compare the effect of a price change of gasoline in Europe versus the United States, there is a complicated conversion between gallons per dollar and liters per euro. This is one of the reasons why economists often use relative changes in percentages, or elasticity. Another reason is that elasticity is more than just the slope of the function: It is the slope of a function in a coordinate space, that is, a line with a constant slope will have different elasticity at various points.
Let's do an example calculation. We have said that one way of calculating elasticity is the percentage change in quantity over the percentage change in price. So, if the price moves from $1.00 to $1.05, and the quantity supplied goes from 100 pens to 102 pens, the slope is 2/0.05 or 40 pens per dollar. Since the elasticity depends on the percentages, the quantity of pens increased by 2%, and the price increased by 5%, so the elasticity is 2/5 or 0.4.
Since the changes are in percentages, changing the unit of measurement or the currency will not affect the elasticity. If the quantity demanded or supplied changes a lot when the price changes a little, it is said to be elastic. If the quantity changes little when the prices changes a lot, it is said to be inelastic. An example of perfectly inelastic supply, or zero elasticity, is represented as a vertical supply curve. (See that section below)
Elasticity in relation to variables other than price can also be considered. One of the most common to consider is income. How would the demand for a good change if income increased or decreased? This is known as the income elasticity of demand. For example, how much would the demand for a luxury car increase if average income increased by 10%? If it is positive, this increase in demand would be represented on a graph by a positive shift in the demand curve, because at all price levels, a greater quantity of luxury cars would be demanded.
Another elasticity that is sometimes considered is the cross elasticity of demand, which measures the responsiveness of the quantity demanded of a good to a change in the price of another good. This is often considered when looking at the relative changes in demand when studying complement and substitute goods. Complement goods are goods that are typically utilized together, where if one is consumed, usually the other is also. Substitute goods are those where one can be substituted for the other, and if the price of one good rises, one may purchase less of it and instead purchase its substitute.
Cross elasticity of demand is measured as the percentage change in demand for the first good that occurs in response to a percentage change in price of the second good. For an example with a complement good, if, in response to a 10% increase in the price of fuel, the quantity of new cars demanded decreased by 20%, the cross elasticity of demand would be −20%/10% or, −2.
Vertical supply curve
It is sometimes the case that the supply curve is vertical: that is the quantity supplied is fixed, no matter what the market price. For example, the amount of land in the world can be considered fixed. In this case, no matter how much someone would be willing to pay for a piece of land, the extra cannot be created. Also, even if no one wanted all the land, it still would exist. These conditions create a vertical supply curve, giving it zero elasticity (i.e., no matter how large the change in price, the quantity supplied will not change).
In the short run near vertical supply curves are even more common. For example, if the Super Bowl is next week, increasing the number of seats in the stadium is almost impossible. The supply of tickets for the game can be considered vertical in this case. If the organizers of this event underestimated demand, then it may very well be the case that the price that they set is below the equilibrium price. In this case there will likely be people who paid the lower price who only value the ticket at that price, and people who could not get tickets, even though they would be willing to pay more. If some of the people who value the tickets less sell them to people who are willing to pay more (i.e., scalp the tickets), then the effective price will rise to the equilibrium price.
The graph below illustrates a vertical supply curve. When the demand 1 is in effect, the price will be p1. When demand 2 is occurring, the price will be p2. Notice that at both values the quantity is Q. Since the supply is fixed, any shifts in demand will only affect price.
Other market forms
In a situation in which there are many buyers but a single monopoly supplier that can adjust the supply or price of a good at will, the monopolist will adjust the price so that his profit is maximized given the amount that is demanded at that price. This price will be higher than in a competitive market. A similar analysis using supply and demand can be applied when a good has a single buyer, a monopsony, but many sellers.
Where there are both few buyers or few sellers, the theory of supply and demand cannot be applied because both decisions of the buyers and sellers are interdependent—changes in supply can affect demand and vice versa. Game theory can be used to analyze this kind of situation. (See also oligopoly.)
The supply curve does not have to be linear. However, if the supply is from a profit-maximizing firm, it can be proven that supply curves are not downward sloping (i.e., if the price increases, the quantity supplied