![\"Newton\u2019s](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/newton-picture-2.webp\")
<\/p>\n\u0641\u06cc\u0632\u06cc\u06a9: \u0642\u0648\u0627\u0646\u06cc\u0646 \u062d\u0631\u06a9\u062a \u0646\u06cc\u0648\u062a\u0646 \u0648 \u06af\u0631\u0627\u0646\u0634 \u062c\u0647\u0627\u0646\u06cc<\/p>\n
<\/p>\n
\u0641\u0627\u06cc\u0644 \u0635\u0648\u062a\u06cc \u0645\u0648\u062c\u0648\u062f \u0646\u06cc\u0633\u062a<\/p>\n
Some of the most important ideas in physics are the laws of motion<\/strong> and of universal gravitation<\/strong>. These laws were discovered during the 1660s by Isaac Newton, an English mathematician and physicist. The three laws of motion and the law of universal gravitation provided a crucial <\/strong>starting point for later discoveries in theoretical physics.<\/p>\n Let us first consider Newton’s three laws of motion. The first law of motion states that every object in a uniform<\/strong> state of motion tends to remain in that state of motion unless an external force is appli<\/strong>ed to it. This law is also known as the law of inertia<\/strong>. Newton’s first law means that objects tend to maintain their current velocity<\/strong>: objects at rest tend to stay at rest, and objects in motion tend to stay in motion. This law seems to contradict <\/strong>common sense, because the objects we see tend to slow down unless a force is applied to them; however, this deceleration is due to<\/strong> the force of friction<\/strong> that is caused by the air, the water, or the ground. If we could study objects moving in a vacuum<\/strong>, those objects would not slow down at all. The second law of motion explains the relation between the force applied to an object, the mass <\/strong>of an object, and the acceleration of an object.<\/p>\n According to Newton’s second law, the force required to cause a given amount of acceleration <\/strong>of an object of a given mass can be calculated by multiplying the acceleration of the object by the mass of the object. In other words, the force, F, equals the mass, m, times the acceleration, a. It is easy to see how this law works. If you want to cause a heavy car to increase or decrease its speed very suddenly, you must apply a very strong force. If you want to cause a lighter car to increase or decrease its speed quite gradually, you need to apply much less force. The third law of motion states that for every action, there is an equal and opposite reaction. One of the important applications of this idea can be seen in the flight of rockets. When a rocket expel<\/strong>s hot, expand<\/strong>ing gases from its tail, the backward force of those gases propel<\/strong>s the rocket forward. Newton realized that the second law of motion could help to explain why objects, such as apples in an apple tree, tend to fall to the earth, and why the moon is held in orbit around the earth.<\/p>\n Newton discovered the law of universal gravitation, which can be summarized as follows: every object in the universe attracts every other object in the universe with a force that is proportional<\/strong> to the product of their masses and inversely <\/strong>proportional to the distance between them. This law has many important implication<\/strong>s for our understanding of the world around us. One of these involves the tide<\/strong>s: we can understand the rising and falling of ocean levels by considering the gravitational forces applied by the moon and the sun. Newton’s laws have served as the foundation for physics and engineering since the 17th century. In the next article, we will discuss the revolutionary discoveries made by physicists during the 20th century.<\/p>\n motion<\/p>\n source 2 gravitation<\/p>\n source 2 crucialsource 1 Usage note: vitalSaying that something is necessary<\/strong>It is vital <\/strong>that journalists can verify the accuracy of their reports. Usage note: essentialvital<\/strong>crucial<\/strong>critical<\/strong>decisive<\/strong>indispensable<\/strong>These words all describe somebody\/something that is extremely important and completely necessary because a particular situation or activity depends on them. essential or vital?These words have the same meaning but there can be a slight difference in tone. Essential<\/strong> is used to state a fact or opinion with authority. Vital<\/strong> is often used when there is some anxiety felt about something, or a need to persuade somebody that a fact or opinion is true, right or important. Vital<\/strong> is less often used in negative statements: It was vital to show that he was not afraid. Money is not vital to happiness. crucial or critical?These words have the same meaning but there can be a slight difference in context. Critical <\/strong>is often used in technical matters of business or science; crucial <\/strong>is often used to talk about matters that may cause anxiety or other emotions. source 2 uniform source 2 apply<\/p>\n source 2 inertia<\/p>\n source 2 velocity<\/p>\n source 2 contradict<\/p>\n source 2 due to source 1 Some people think that it is more correct to use owing to<\/strong> to mean \u2018because of\u2019 after a verb or at the beginning of a clause, as due <\/strong>is an adjective.<\/p>\n Usage note: because ofExplaining reasons<\/strong>The number of people with diabetes is growing, partly because of<\/strong> an increase in levels of obesity. source 2 WORD CHOICE: owing to, due to, because of, thanks to<\/strong>Owing to<\/strong> and due to<\/strong> are slightly formal. They are often used in official notices and public statements friction<\/p>\n source 2 vacuumsource 1 source 2 mass<\/p>\n Weight is used in non-technical language for this meaning<\/p>\n source 2 acceleration<\/p>\n source 2 expel<\/p>\n expandsource 1 source 2 propel<\/p>\n source 2 proportionalsource 1 source 2 inversely source 2 implicationsource 1
\n
\n![\"motion\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/motion-2.webp\")
\nsource 1
\nthe act or process of moving or the way something moves
\nNewton’s laws of motion
\nThe swaying motion of the ship was making me feel seasick.
\n(formal) Do not alight while the train is still in motion (= moving).
\nRub the cream in with a circular motion.<\/p>\n
\nthe process of moving or the way that someone or something moves
\nmotion of <\/strong>the motion of the planets
\nThe rocking motion of the boat made Sylvia feel sick.
\nNewton’s first law of motion<\/p>\n![\"gravitation\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/gravitation-2.webp\")
\nsource 1
\na force of attraction that causes objects to move towards each other<\/p>\n
\nthe force that causes two objects such as planets to move towards each other because of their mass [\u21aa gravity]:
\nNewton’s law of gravitation<\/p>\n
\nextremely important, because it will affect other things
\nSynonym:<\/strong> critical, essential
\na crucial factor\/issue\/decision
\ntopics of crucial importance
\nThe next few weeks are going to be crucial.
\ncrucial to\/for something<\/strong>
\nWinning this contract is crucial to the success of the company.
\ncrucial that\u2026<\/strong>
\nIt is crucial that we get this right.
\nParents play a crucial role in preparing their child for school.
\nHe wasn’t there at the crucial moment (= when he was needed most).<\/p>\n
\nJournalists play a vital\/crucial<\/strong> role in educating the public.
\nPublic trust is a crucial<\/strong> issue for all news organizations.
\nThe ability to write well is essential<\/strong> for any journalist.
\nThe Internet has become an indispensable<\/strong> tool for reporters.
\nIn journalism, accuracy is paramount<\/strong>. \/ \u2026is of paramount importance<\/strong>.
\nIt is imperative that<\/strong> journalists maintain the highest possible standards of reporting.<\/p>\n
\nessential<\/strong> extremely important and completely necessary, because without it something cannot exist, be made or be successful: Experience is essential for this job.
\nvital <\/strong>essential: The police play a vital role in our society.<\/p>\n
\ncrucial <\/strong>extremely important because a particular situation or activity depends on it: It is crucial that we get this right.
\ncritical <\/strong>extremely important because a particular situation or activity depends on it: Your decision is critical to our future.<\/p>\n
\ndecisive<\/strong> of the greatest importance in affecting the final result of a particular situation: She has played a decisive role in the peace negotiations.
\nindispensable<\/strong> essential; too important to be without: Cars have become an indispensable part of our lives.
\nessential\/vital\/crucial\/critical\/decisive\/indispensable for <\/strong>something
\nessential\/vital\/crucial\/critical\/indispensable to <\/strong>something
\nessential\/vital\/crucial\/critical that\u2026<\/strong>essential\/vital\/crucial\/critical to do something<\/strong>a(n) essential\/vital\/crucial\/critical\/decisive\/indispensable part\/factor<\/strong>of vital\/crucial\/critical\/decisive importance<\/strong>absolutely <\/strong>essential\/vital\/crucial\/critical\/decisive\/indispensable<\/p>\n
\nsomething that is crucial is extremely important, because everything else depends on it
\ncrucial to <\/strong>This aid money is crucial to the government’s economic policies.
\ncrucial in\/to doing something<\/strong>
\nThe work of monks was crucial in spreading Christianity.
\nplay a crucial role\/part in something <\/strong>The city of Mycenae played a crucial role in the history of Greece.
\nThe conservation of tropical forests is of crucial importance.<\/p>\n
\n![\"uniform\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/uniform-2.webp\")
\nsource 1
\nnot varying; the same in all parts and at all times
\nuniform rates of pay
\nThe walls were a uniform grey.
\nGrowth has not been uniform across the country.
\nuniform lines of terraced houses (= they all looked the same)<\/p>\n
\nbeing the same in all its parts or among all its members:
\nGrade A eggs must be of uniform size.<\/p>\n![\"apply\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/apply-2.webp\")
\nsource 1
\nto press on something hard with your hand, foot, etc. to make something work or have an effect on something
\napply something <\/strong>to apply the brakes (of a vehicle)
\napply something to something <\/strong>Pressure applied to the wound will stop the bleeding.<\/p>\n
\nto make something such as a piece of equipment operate, usually by pushing or pressing something:
\napply the brakes<\/p>\n![\"inertia\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/inertia-2.webp\")
\nsource 1
\na property (= characteristic) of matter (= a substance) by which it stays still or, if moving, continues moving in a straight line unless it is acted on by a force outside itself<\/p>\n
\nthe force that keeps an object in the same position or keeps it moving until it is moved or stopped by another force<\/p>\n![\"velocity\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/velocity-2.webp\")
\nsource 1
\nthe speed of something in a particular direction
\nthe velocity of light
\nto gain\/lose velocity
\na high-velocity rifle<\/p>\n
\ntechnical the speed of something that is moving in a particular direction:
\nthe velocity of light
\nThe speedboat reached a velocity of 120 mph.
\na high velocity bullet<\/p>\n![\"contradict\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/contradict-2.webp\")
\nsource 1
\ncontradict something\/ contradict each other <\/strong>(of statements or pieces of evidence)
\nto be so different from each other that one of them must be wrong
\nThe two stories contradict each other.
\nThis version of events was contradicted by eye-witness reports.<\/p>\n
\nif one statement, story etc contradicts another, the facts in it are different so that both statements cannot be true:
\nThe witness statements contradict each other and the facts remain unclear.<\/p>\n
\ndue to something\/somebody <\/strong>caused by somebody\/something; because of somebody\/something
\nThe team’s success was largely due to her efforts.
\nMost of the problems were due to human error.
\nThe project had to be abandoned due to a lack of government funding.
\nDue to staff shortages, we are unable to offer a full buffet service on this train.<\/p>\n
\nThe number of overweight children has increased dramatically in recent years, largely as a result of <\/strong>changes in diet and lifestyle.
\nThe increase in childhood obesity is largely due to\/the result of <\/strong>changes in lifestyle and diet over the last twenty years.
\nMany obese children are bullied at school on account of <\/strong>their weight.
\nPart of the problem with treating childhood obesity stems from <\/strong>the fact that parents do not always recognize that their children are obese.
\nChildhood obesity may be caused by <\/strong>genetic factors, as well as environmental ones.
\nLanguage Banks at cause, consequently, therefore<\/p>\n
\nbecause of something:
\nThe court of inquiry ruled that the crash was due to pilot error.
\nShe has been absent from work due to illness.
\nThe restaurant’s success was due largely to its new manager.
\nAttendance at the meeting was small, due in part to (=partly because of) the absence of teachers.<\/p>\n
\nOwing to bad weather, this morning’s flight will be delayed.
\nHe is retiring due to ill health.
\n!! Owing to<\/strong> and due to<\/strong> are prepositions (they come immediately before a noun). They are not conjunctions (they cannot connect two parts of a sentence)
\nI had to wait hours because the plane was delayed (NOT I had to wait hours owing to the plane was delayed).
\nIn spoken English, it is more usual to use because of<\/strong> than owing to<\/strong> or due to <\/strong>All my clothes got wet because of the storm (NOT owing to the storm).
\nThanks to<\/strong> is used to explain why something good has happened
\nThanks to the success of his first album, he is now a wealthy man.<\/p>\n![\"friction\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/friction-2.webp\")
\nsource 1
\nthe resistance (= the force that stops something moving) of one surface to another surface or substance moving over or through it
\nThe force of friction slows the spacecraft down as it re-enters the earth’s atmosphere.<\/p>\n
\nthe natural force that prevents one surface from sliding easily over another surface:
\nPutting oil on both surfaces reduces friction.<\/p>\n
\na space that is completely empty of all substances, including all air or other gas
\na vacuum pump (= one that creates a vacuum )
\nvacuum-packed foods (= in a package from which most of the air has been removed)<\/p>\n
\na space that is completely empty of all gas, especially one from which all the air has been taken away<\/p>\n![\"mass\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/mass-2.webp\")
\nsource 1
\nthe quantity of material that something contains
\ncalculating the mass of a planet<\/p>\n
\nthe amount of material in something:
\nThe sun makes up 99.9% of the mass of our solar system.<\/p>\n![\"acceleration\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/acceleration-2.webp\")
\nsource 1
\nthe rate at which the velocity (= speed in a particular direction) of an object changes
\nacceleration caused by gravity<\/p>\n
\nthe rate at which the speed of an object increases<\/p>\n![\"expel\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/expel-2.webp\")
\nto force air or water out of a part of the body or from a container
\nto expel air from the lungs<\/p>\n
\nto become greater in size, number or importance; to make something greater in size, number or importance
\nMetals expand when they are heated.
\nStudent numbers are expanding rapidly.
\nA child’s vocabulary expands through reading.
\nThe waist expands to fit all sizes.
\nexpand something <\/strong>In breathing the chest muscles expand the rib cage and allow air to be sucked into the lungs.
\nThe new system expanded the role of family doctors.
\nThere are no plans to expand the local airport.
\nOpposite:<\/strong> contract<\/p>\n
\nto become larger in size, number, or amount, or to make something become larger [\u21aa expansion; \u2260 contract]:
\nWater expands as it freezes.
\nSydney’s population expanded rapidly in the 1960s.
\nexercises that expand the chest muscles
\nhis expanding waistline<\/p>\n![\"propel\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/propel-2.webp\")
\nsource 1
\npropel something (+ adverb\/preposition) <\/strong>to move, drive or push something forward or in a particular direction
\nmechanically propelled vehicles
\na boat propelled only by oars
\nHe succeeded in propelling the ball across the line.<\/p>\n
\nto move, drive, or push something forward [\u21aa propulsion]:
\na boat propelled by a small motor
\nOne of our students was unable to propel her wheelchair up the ramp.
\npropel yourself along\/through etc <\/strong>She used the sticks to propel herself along.<\/p>\n
\nproportional (to something)<\/strong>
\nof an appropriate size, amount or degree in comparison with something
\nSalary is proportional to years of experience.
\nThe number of teachers appointed is proportional to the total number of students.
\nto be directly\/inversely proportional to something<\/p>\n
\nsomething that is proportional to something else is in the correct or most suitable relationship to it in size, amount, importance etc [\u2260 disproportionate]
\nproportional to <\/strong>The punishment should be proportional to the crime.
\nThe fee charged by the realtor is directly proportional to the price of the property.
\na proportional increase in costs<\/p>\n
\n![\"inverse\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/inverse-2.webp\")
\nsource 1
\ninverse<\/strong>opposite in amount or position to something else
\nA person’s wealth is often in inverse proportion to their happiness (= the more money they have, the less happy they are).
\nThere is often an inverse relationship between the power of the tool and how easy it is to use.
\ninversely <\/strong>adverb
\nWe regard health as inversely related to social class.<\/p>\n
\nexactly opposite
\ninversely adverb<\/p>\n
\na possible effect or result of an action or a decision
\nThey failed to consider the wider implications of their actions.
\nThe development of the site will have implications for the surrounding countryside.<\/p>\n
![\"tide\"](\"https:\/\/salamzaban.com\/conversation\/wp-content\/uploads\/2010\/11\/tide-water-ocean-2.webp\")