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A diagram is shown in which time progresses along the vertical y axis and distance along the horizontal x axis. Protons and neutrons are shown approaching each other, exchanging a virtual pion, then moving apart.
The image shows a Feynman diagram for the exchange of a π + size 12{π rSup { size 8{+{}} } } {} between a proton and a neutron, carrying the strong nuclear force between them. This diagram represents the situation shown more pictorially in [link] .

The relative strengths of the forces given in the [link] are those for the most common situations. When particles are brought very close together, the relative strengths change, and they may become identical at extremely close range. As we shall see in GUTs: the Unification of Forces , carrier particles may be altered by the energy required to bring particles very close together—in such a manner that they become identical.

Making connections: why you stay on the earth, but do not fall through

You are familiar with gravity pulling you towards the Earth. It's why when you jump, you come back down. In this action, and at distances and speeds that we experience in our everyday lives, gravity is the only one of the four fundamental forces that has such an obvious effect on us.

Electromagnetism is vital for our society to run, but due to your body having the same (or very nearly the same) number of positive and negative charges, it doesn't usually have as much of an effect on us. Except for one very important feature: the electrons in the bottom of your feet experience a mutually repulsive force with the electrons in the material you stand on. This is what keeps us from falling into the planet, and also allows us to push on other objects and generally interact with them.

These electromagnetic forces are dominant in the electron shells of an atom, and also the interaction of the electrons with the nucleus. However, within the nucleus, the electrostatic repulsion of the protons would break the nucleus apart if it were not for the strong force, which holds the nucleus together. At even smaller scales, within nucleons such as protons and neutrons, the weak force is responsible for nuclear decays.

The relative strengths of the forces given in the [link] are those for the most common situations. When particles are brought very close together, the relative strengths change, and they may become identical at extremely close range. As we shall see in GUTs: the Unification of Forces , carrier particles may be altered by the energy required to bring particles very close together—in such a manner that they become identical.

Test prep for ap courses

Two intact (not ionized) hydrogen atoms are 10 cm apart. Which of the following are true?

  1. Gravity, though very weak, is acting between them.
  2. The neutral charge means the electromagnetic force between them can be ignored.
  3. The range is too long for the strong force to be involved.
  4. All of the above.

(d)

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Explain why we only need to concern ourselves with gravitational force to describe the orbit of the Earth around the Sun.

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Consider four forces: the gravitational force between the Earth and the Sun; the electrostatic force between the Earth and the Sun; the gravitational force between the proton and electron in a hydrogen atom, and the electrostatic force between the proton and electron in a hydrogen atom. What is the proper ordering of the magnitude of these forces, from greatest to least?

  1. gravity, Earth-Sun; electrostatic, Earth-Sun; gravity, hydrogen; electrostatic, hydrogen
  2. electrostatic, Earth-Sun; gravity, Earth-Sun; electrostatic, hydrogen; gravity, hydrogen
  3. gravity, Earth-Sun; gravity, hydrogen; electrostatic, hydrogen; electrostatic, Earth-Sun
  4. gravity, Earth-Sun; electrostatic, hydrogen; gravity, hydrogen; electrostatic, Earth-Sun

(d)

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Deep within a nucleon, which is the stronger force between two quarks, gravity or the weak force? Why do you think so?

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Consider the Earth-Moon system. If we were to place equal charges on the Earth and the Moon, how large would they need to be for the electrostatic repulsion to counteract the gravitational attraction?

  1. 5.1×10 13 C
  2. 5.7×10 13 C
  3. 6.7×10 13 C
  4. 3.3×10 27 C

(b)

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What is the strength of the magnetic field created by the orbiting Moon, at the center of the orbit, in the system in the previous problem? (Treat the charge going around in orbit as a current loop.) How does this compare with the strength of the Earth's intrinsic magnetic field?

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An atomic nucleus consists of positively charged protons and neutral neutrons, so the electrostatic repulsion should destroy it by making the protons fly apart. This doesn't happen because:

  1. The strong force is ~100 times stronger than electromagnetism.
  2. The weak force generates massive particles that hold it together.
  3. Electromagnetism is sometimes attractive.
  4. Gravity is always attractive.

(a)

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The atomic number of an atom is the number of protons in that atom's nucleus. Make a prediction as to what happens to electromagnetic repulsion as the atomic number gets larger. Then, make a further prediction about what this implies about the number of neutrons in heavy nuclei.

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Summary

  • The four basic forces and their carrier particles are summarized in the [link] .
  • Feynman diagrams are graphs of time versus position and are highly useful pictorial representations of particle processes.
  • The theory of electromagnetism on the particle scale is called quantum electrodynamics (QED).

Problems&Exercises

(a) Find the ratio of the strengths of the weak and electromagnetic forces under ordinary circumstances.

(b) What does that ratio become under circumstances in which the forces are unified?

(a) 10 11 size 12{"10" rSup { size 8{ - "11"} } } {} to 1, weak to EM

(b) 1 to 1

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The ratio of the strong to the weak force and the ratio of the strong force to the electromagnetic force become 1 under circumstances where they are unified. What are the ratios of the strong force to those two forces under normal circumstances?

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Questions & Answers

differentiate between demand and supply giving examples
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In economics, a perfect market refers to a theoretical construct where all participants have perfect information, goods are homogenous, there are no barriers to entry or exit, and prices are determined solely by supply and demand. It's an idealized model used for analysis,
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When MP₁ becomes negative, TP start to decline. Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of lab
Kelo
Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of labour (APL) and marginal product of labour (MPL)
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What is different between quantity demand and demand?
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Quantity demanded refers to the specific amount of a good or service that consumers are willing and able to purchase at a give price and within a specific time period. Demand, on the other hand, is a broader concept that encompasses the entire relationship between price and quantity demanded
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Economic growth as an increase in the production and consumption of goods and services within an economy.but Economic development as a broader concept that encompasses not only economic growth but also social & human well being.
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In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities, where neither p
Cornelius
In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities,
Cornelius
Suppose a consumer consuming two commodities X and Y has The following utility function u=X0.4 Y0.6. If the price of the X and Y are 2 and 3 respectively and income Constraint is birr 50. A,Calculate quantities of x and y which maximize utility. B,Calculate value of Lagrange multiplier. C,Calculate quantities of X and Y consumed with a given price. D,alculate optimum level of output .
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Answer
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the market for lemon has 10 potential consumers, each having an individual demand curve p=101-10Qi, where p is price in dollar's per cup and Qi is the number of cups demanded per week by the i th consumer.Find the market demand curve using algebra. Draw an individual demand curve and the market dema
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suppose the production function is given by ( L, K)=L¼K¾.assuming capital is fixed find APL and MPL. consider the following short run production function:Q=6L²-0.4L³ a) find the value of L that maximizes output b)find the value of L that maximizes marginal product
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types of unemployment
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What is the difference between perfect competition and monopolistic competition?
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Source:  OpenStax, College physics for ap® courses. OpenStax CNX. Nov 04, 2016 Download for free at https://legacy.cnx.org/content/col11844/1.14
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