FORCES FORCES FIND OUT MORE From the movements of the planets to the energy produced inside atoms, everything that happens in the Universe is ultimately caused by forces. A force is a push or pull that can make an object move or TURN around. The bigger the force, the more movement it can produce. When two or more forces act together on an object, their effects are COMBINED . Sometimes the forces add together to make a larger force, and sometimes they cancel each other out. NEWTONS Forces are measured in units called newtons (N), named after English scientist Sir Isaac Newton. The size of a force can be measured using a device called a force meter or newtonmeter. As the load pulls on the hook, it stretches a spring to give a reading on the scale. On Earth, the force of gravity on 1 kg (2.2 lb) is 9.8 newtons. TURNING FORCES If an object is fixed at one point and can rotate around it, that point is called a pivot. If a force acts on the object, the object turns around the pivot. The turning force is called a torque and the effect it produces is called a moment. The bigger the force, the greater the moment.

The moment also increases if the force acts at a greater distance from the pivot. A wheelbarrow is free to pivot around the large wheel at the front. When the worker lifts the handles, the force causes the entire wheelbarrow to swing upwards and turn around the wheel. The long body and handles of a wheelbarrow increase the turning effect and make it easier to tip out a heavy load. INCREASING MOMENTS It is easier to unscrew a nut with a spanner than with your fingers, because the spanner’s long handle increases the turning effect or moment of the force. The size of a moment is equal to the force used times the distance from the pivot on which it acts. If you use a spanner twice as long, you double the moment, and the nut is twice as easy to turn. COMBINED FORCES When forces act in the same direction, they combine to make a bigger force. When they act in opposite directions, they can cancel one another out. If the forces acting on an object balance, the object does not move, but may change shape. If the forces combine to make an overall force in one direction, the object moves in that direction.

SUPPORTING A BRIDGE A suspension bridge has to support the weight of its own deck, plus the weight of the vehicles that go across it. The deck of the bridge hangs from huge steel cables suspended over giant pillars. The cables and pillars are arranged so that there is no overall force in any direction. A bridge stays up because the forces on it are balanced and cancel one another out. FIND OUT MORE Moment - definition of moment by The Free Dictionary Moment - definition of moment by The Free Dictionary 1. A brief, indefinite interval of time. 2. a. A specific point in time, especially the present time: He is not here at the moment. b. A point in time that is gratifying or noteworthy: Even working on a dictionary has its moments. c. An occasion affording an opportunity: viewed the blunder as a teachable moment. 3. A particular period of importance, influence, or significance in a series of events or developments: a great moment in history; waiting for her big moment. 4. Outstanding significance or value; importance: a discovery of great moment. 5.

A brief period of time that is characterized by a quality, such as excellence, suitability, or distinction: a lackluster performance that nevertheless had its moments. 6. Philosophy a. An essential or constituent element, as of a complex idea. b. A phase or aspect of a logically developing process. 7. Abbr. M Physics a. The product of a quantity, such as force or mass, and its perpendicular distance from a reference point. b. The tendency to cause rotation about a point or axis. 8. Statistics The expected value of a positive integer power of a random variable. The first moment of a random variable is the mean of its probability distribution. [Middle English, from Old French, from Latin mōmentum, from *movimentum; see momentum.] Synonyms: moment, instant, minute1, second1, jiffy, flash These nouns denote a brief interval of time. A moment is an indeterminately short but significant period: I'll be with you in a moment. Instant is a period of time almost too brief to detect; it implies haste: He hesitated for just an instant. Minute is often interchangeable with moment and second with instant: The alarm will ring any minute.

I'll be back in a second. Jiffy and flash are somewhat informal and usually combine with in a; in a jiffy means in a short space of time, while in a flash suggests the almost imperceptible duration of a flash of light: He went to the store but will be back in a jiffy. She finished the job in a flash. See Also Synonyms at importance . moment 1. a short indefinite period of time: he'll be here in a moment. 2. a specific instant or point in time: at that moment the doorbell rang. 3. the moment the present point of time: at the moment it's fine. 4. import, significance, or value: a man of moment. 5. (General Physics) physics a. a tendency to produce motion, esp rotation about a point or axis b. the product of a physical quantity, such as force or mass, and its distance from a fixed reference point. See also moment of inertia 6. (Statistics) statistics the mean of a specified power of the deviations of all the values of a variable in its frequency distribution.

The power of the deviations indicates the order of the moment and the deviations may be from the origin (giving a moment about the origin) or from the mean (giving a moment about the mean) [C14: from Old French, from Latin mōmentum, from movēre to move] mo•ment n. 1. an indefinitely short period of time; instant. 2. the present time or any other particular time (usu. prec. by the): He is busy at the moment. 3. a definite period or stage, as in a course of events: at that moment in history Rome was a republic. 4. importance or consequence: a decision of great moment. 5. a time or period of success, excellence, satisfaction, etc.: My job has its moments. 6. Statistics. the mean or expected value of the product formed by multiplying together a set of one or more variates or variables each to a specified power. 7. Mech. a. a tendency to produce motion, esp. about an axis. b. the product of a physical quantity and its directed distance from an axis.

[1300–50; Middle English < Latin mōmentum motion, cause of motion, hence, influence, essential factor, moment of time =mō- (variant s. of movēre to move ) + -mentum -ment ] syn: See importance. moment extemporaneous , impromptu - Extemporaneous means "prepared in advance and carried out with few or no notes," while impromptu means "totally unprepared, performed on the spur of the moment"—but this distinction has been all but lost. moment , momentum - Latin momentum, from movere, "move," and -mentum, is the source of moment and momentum, which first meant "moving power." moment of truth - A translation of a Spanish expression referring to the time of the final sword thrust in a bullfight. momentarily , presently - Momentarily means "in a moment"; presently means "soon" or "shortly." moment In air transport, the weight of a load multiplied by its distance from a reference point in the aircraft. moment A moment is a very short period of time. She hesitated for only a moment. A few moments later he heard footsteps. 2.

'the moment' The moment is often used as a conjunction to say that something happens or is done at the same time as something else, or immediately after it. The moment I heard the news, I rushed over to her house. When you use the moment in this way to talk about the future, you use the present simple after it. Don't use a future form. The moment he arrives, ask him to come and see me. 3. 'at the moment' At the moment means now, at the present time. I'm very busy at the moment. Be Careful! Don't say 'I'm very busy in the moment' or 'I'm very busy in this moment'. 4. 'in a moment' You can use in a moment to mean 'soon'. Wait there  I'll be back in a moment. moment The turning effect produced by a force acting around a point.

ThesaurusAntonymsRelated WordsSynonymsLegend: climax , culmination - the decisive moment in a novel or play; "the deathbed scene is the climax of the play" point in time , point - an instant of time; "at that point I had to leave" eleventh hour , last minute - the latest possible moment; "money became available at the eleventh hour"; "at the last minute the government changed the rules" moment of truth - a crucial moment on which much depends moment of truth - the moment in a bullfight when the matador kills the bull pinpoint - a very brief moment; "they were strangers sharing a pinpoint of time together" time - a suitable moment; "it is time to go" psychological moment - the most appropriate time for achieving a desired effect 2.

moment - an indefinitely short time; "wait just a moment"; "in a mo"; "it only takes a minute"; "in just a bit" mo , second , minute , bit time - an indefinite period (usually marked by specific attributes or activities); "he waited a long time"; "the time of year for planting"; "he was a great actor in his time" instant , jiffy , New York minute , split second , trice , twinkling , wink , blink of an eye , heartbeat , flash - a very short time (as the time it takes the eye to blink or the heart to beat); "if I had the chance I'd do it in a flash" 3. moment - at this time; "the disappointments of the here and now"; "she is studying at the moment" nowadays , present - the period of time that is happening now; any continuous stretch of time including the moment of speech; "that is enough for the present"; "he lives in the present with no thought of tomorrow" 4.

moment - having important effects or influence; "decisions of great consequence are made by the president himself"; "virtue is of more moment than security"; "that result is of no consequence" matter - (used with negation) having consequence; "they were friends and it was no matter who won the games" significance - the quality of being significant; "do not underestimate the significance of nuclear power" hell to pay - dire consequences; "when the pig ran away there was hell to pay" 5. moment - a turning force produced by an object acting at a distance (or a measure of that force) force - (physics) the influence that produces a change in a physical quantity; "force equals mass times acceleration" moment of inertia - the tendency of a body to resist angular acceleration moment of a couple - given two equal and opposite forces, the product of the force and the distance between them dipole moment - the moment of a dipole 6.

moment - the n-th moment of a distribution is the expected value of the n-th power of the deviations from a fixed value statistics - a branch of applied mathematics concerned with the collection and interpretation of quantitative data and the use of probability theory to estimate population parameters statistic - a datum that can be represented numerically second moment - the expected value of the square of the deviations of a random variable from the point of origin variance - the second moment around the mean; the expected value of the square of the deviations of a random variable from its mean value moment noun 3. importance , concern , value , worth , weight , import , consequence , substance , significance , gravity , seriousness , weightiness I was glad I had nothing of great moment to do that afternoon.

Quotations "in the twinkling of an eye" Bible: I Corinthians moment لَـحْظَةٌ لَحْظَه مُعَيَّنَهلَحْظَه، وَقت قَصير، دَقيقَه okamžikchvílemoment síly a moment ago → hace un momento they should be arriving any moment (now) → deberían llegar ahorita (LAm) or de un momento a otro I could lose my job at any moment → podría perder mi trabajo en cualquier momento at this/that moment → en este/ese momento , en este/ese instante at this moment in time → en este mismo momento for the moment → por el momento , por lo pronto he didn't hesitate for a moment → no vaciló ni un momento or instante not for a or one moment did I believe it → no me lo creí ni por un momento I'm not saying for a moment you're wrong → no digo que no tengas razón ni mucho menos not for a moment did I think that → en ningún momento pensaba que ...

from the moment I saw him → desde el momento en que lo vi from moment to moment → al momento from that moment on → desde entonces , desde ese or aquel momento the play has its moments → la obra tiene sus momentos yes, in a moment! → ¡sí en seguida ! in moments, I was asleep → en seguida me quedé dormido just a moment! → ¡un momento ! I've just this moment heard → acabo de enterarme at the last moment → a última hora , en el último momento to leave things until the last moment → dejar las cosas hasta última hora , dejarlo todo para lo último the next moment he collapsed → al instante se desplomó he was weeping one moment, laughing the next → tan pronto lloraba como se reía the man of the moment → el hombre del momento one moment! → ¡un momento !

I was waiting for the right moment to tell him → estaba esperando el momento adecuado or oportuno para decírselo it won't take a moment → no tardará ni un momento , es cosa de un momento tell me the moment he arrives → avísame en cuanto llegue I did it in a moment of weakness → lo hice en un momento de debilidad see also heat A2 see also live 1 A1 see also odd 2 see also spur A3 AS SOON AS 2. (Phys) → momento m moment of inertia → momento m de inercia 3. (frm) (= importance) → importancia f of great/little moment → de gran /poca importancia moment at any moment → à tout moment any moment now → d'un moment à l'autre They'll be arriving any moment now → Ils vont arriver d'un moment à l'autre. at the last moment → au dernier moment at the present moment → en ce moment même at this moment in time → au moment où je vous parle (= exact time) → moment m the moment (that) ... → à l'instant où ...

The moment I closed my eyes, I fell asleep → À l'instant où j'ai fermé les yeux , je me suis endormi . at that moment → à ce moment (= short time) → moment m Could you wait a moment? → Pouvez-vous attendre un moment ? just a moment! → un instant ! for a moment → pendant un moment She stared at him for a moment → Elle le fixa pendant un moment . it lasted only a moment → cela n'a duré qu'un moment in a moment (= very soon) → dans un instant (= very quickly) → en un instant I'll be back in a moment → Je reviens dans un instant . It all happened in a moment → Cela a été l'affaire d'un instant . within moments (= very soon) → en l'espace d'un instant the next moment (= suddenly) → l'instant d'après not for a moment (= absolutely not) → pas un instant I don't for a moment think (that) ... → Je ne crois pas un instant que ...

moment n → Augenblick m, → Moment m; there were one or two moments when I thought … → ein paar Mal dachte ich …; from moment to moment → zusehends , von Minute zu Minute ; any moment now, (at) any moment → jeden Augenblick ; at any moment (= any time) → jederzeit ; at the moment → im Augenblick , momentan ; at the moment when … → zu dem Zeitpunkt , als …; not at the or this moment → im Augenblick or zurzeit nicht ; at the moment of impact → beim Aufprall , im Augenblick des Aufpralls ; at the last moment → im letzten Augenblick ; at this (particular) moment in time → momentan , augenblicklich ; for the moment → im Augenblick , vorläufig ; for a moment → (für) einen Moment ; for one moment it seemed to have stopped → einen Augenblick lang schien es aufgehört zu haben; not for a or one moment … → nie (mals) …; I didn’t hesitate for a moment → ich habe keinen Augenblick gezögert ; in a moment → gleich; in a moment of madness → in einem

 Anflug von geistiger Umnachtung ; it was all over in a moment or in a few moments → das ganze dauerte nur wenige Augenblicke ; to leave things until the last moment → alles erst im letzten Moment erledigen or machen (inf); half a moment!, one moment!

→ einen Moment !; just a moment!, wait a moment! → Moment mal!; I shan’t be a moment → ich bin gleich wieder da; (= nearly ready) → ich bin gleich so weit ; do it this very moment!

→ tu das auf der Stelle !; I have just this moment heard about it → ich habe es eben or gerade erst erfahren ; we haven’t a moment to lose → wir haben keine Minute zu verlieren ; not a moment too soon → keine Minute zu früh , in letzter Minute ; not a moment’s peace or rest → keine ruhige Minute ; one moment she was laughing, the next she was crying → zuerst lachte sie, einen Moment später weinte sie; the moment it happened → (in dem Augenblick,) als es passierte ; the moment I saw him I knew … → als ich ihn sah , wusste ich sofort …; the moment he arrives there’s trouble → sobald er auftaucht , gibt es Ärger ; tell me the moment he comes → sagen Sie mir sofort Bescheid , wenn er kommt ; the moment of truth → die Stunde der Wahrheit ; he is the man of the moment → er ist der Mann des Tages ; the film has its moments → streckenweise hat der Film was (inf) (Phys) → Moment nt; moment of acceleration/inertia → Beschleunigungs-/Trägheitsmoment nt (= importance) → Bedeutung

 f; of little moment → bedeutungslos , unwichtig moment at the last moment → all'ultimo momento for a or one moment → per un momento not for a or one moment → neanche per un istante in a moment (very soon) → tra un momento (quickly) → in un attimo one moment!, wait a moment!

→ (aspetta) un momento or un attimo ! I won't be a moment → vengo (or torno) subito (I've nearly finished) → faccio subito it won't take a moment → è (solo) questione di un attimo I've just this moment heard about it → l'ho saputo in questo (preciso) istante the moment he arrives → (non) appena arriva from the moment I saw him → dal primo momento in cui l'ho visto the man of the moment → l'uomo del momento "one moment please" (Telec) → "attenda, prego" c. (frm) (importance) → importanza , rilievo moment (ˈməumənt) noun 1. a very short space of time. I'll be ready in a moment; after a few moments' silence.

oomblik لَحْظَه، وَقت قَصير، دَقيقَه кратък отрязък от време momento okamžik der Moment øjeblik στιγμή momento , instante hetk زمان hetki moment , instant רגע क्षण tren, časak pillanat saat augnablik momento 瞬間 찰나 akimirksnis, akimirka moments; brīdis seketika ogenblik øyeblikk moment وخت momento moment, clipă момент ; минута chvíľa, moment trenutek trenutak ögonblick ชั่วครู่ an 片刻 момент; мить لمحہ chốc, lát 片刻，瞬间 2. a particular point in time. At that moment, the telephone rang.

oomblik لَحْظَه مُعَيَّنَه момент momento chvíle der Augenblick øjeblik στιγμή momento , instante hetk هنگام hetki moment , instant רגע किसी क्षण taj tren időpont saat augnablik, andrá momento その時 특정 시점 momentas moments saat ogenblik øyeblikk chwila شيبه momento moment, clipă момент chvíľa trenutek trenutak tidpunkt, ögonblick ชั่วขณะ an 特定 момент; мить کوئی خاص موقع thời điểm 时刻 ˈmomentary adjective lasting for only a moment. a momentary feeling of fear.

tydelike مُؤَقَّت моментен momentâneo chvilkový momentan flygtig στιγμιαίος momentáneo hetkeline انی hetkellinen momentané לְרֶגָע क्षणिक trenutačan pillanatnyi sesaat augnabliks- momentaneo 瞬間の 순간의 akimirką trunkantis, momentalus momentāns; acumirklīgs sejenak kortstondig forbigående chwilowy ناڅاپه momentâneo mo­men­tan, de moment кратковременный chvíľkový trenuten trenutni som varar ett ögonblick, tillfällig ชั่วขณะ bir anlık 片刻的，短暫的 моментальний, миттєвий آنی و فانی thoáng qua 倾刻的 ˈmomentarily ((American) moumənˈte-) adverb momenteel مُؤَقَّتا моментно momentaneamente na okamžik; ihned momentan flygtigt προ

ς στιγμήν momentáneamente silmapilkselt بطور انی hetkellisesti momentanément בְּעוֹד רֶגָע क्षणिक रूप से trenutno pillanatnyilag dalam sesaat í eitt augnablik momentaneamente 瞬間的に 잠시, 잠깐 vieną akimirką, tuoj pat acumirklī sejenak kortstondig om litt, om et øyeblikk; for et øyeblikk chwilowo , nagle په ناڅاپى ډول momentaneamente mo­men­­tan на мгновение; мгновенно na okamih; okamžite trenutno trenutno för ett ögonblick, tillfälligt ชั่วขณะ bir an için 一時，短暫地 моментально لمحہ بھر کو một cách thoáng qua 短暂地 moˈmentous (-ˈmen-) adjective of great importance.

a momentous event.

gewigtig بالِغ الأهَمِّيَّه много важен importante důležitý bedeutsam betydningsfuld βαρυσήμαντος trascendental ülitähtis مهم ikimuistoinen capital חָשׁוּב בְּיוֹתֵר आवश्यक, महत्वपूर्ण važan, znamenit nagy jelentőségű penting þÿðingarmikill, afdrifaríkur importantissimo 重大な 중요한 įsimintinas, reikšmingas svarīgs, nozīmīgs penting zeer belangrijk avgjørende , meget viktig doniosły ارزښتناك importante capital важнейший dôležitý pomemben značajan viktig, betydelsefull มีความหมายสำคัญมาก çok büyük 重大的 важливий بڑی اہمیت کا حامل trọng yếu 重大的 moˈmentously adverb gewigtig بأهَمِّ

يَّةٍ بالِغَه много важно de importância významně bedeutsam betydningsfuldt βαρυσήμαντα de importancia tähtsalt با اهمیت ikimuistoisesti de façon importante בְּחָשִיבוּת महत्वपूर्ण रूप से znamenito jelentősen secara penting á afdrifaríkan hátt in maniera importante ゆゆしく 중요하게 reikšmingai svarīgi, nozīmīgi dengan penting gewichtig avgjørende doniośle ارزښتناك de importância (într-un mod) impre­sionant важно významne pomembno značajno viktigt, betydelsefullt อย่างมีความหมายสำคัญมาก önemli olarak 重大地 важливо عظيم انداز میں một cách trọng yếu 重大地 at the moment at this particular time; now.

She's rather busy at the moment.

op die oomblik في هذه اللحْظَه сега neste momento teď právě im Augenblick for øjeblikket αυτή τη στιγμή de momento, por ahora hetkel در یک لحظه tällä hetkellä en ce moment כַּרֶגָע अब, इस समय u tom trenu pillanatnyilag sekarang, pada waktu ini núna, þessa stundina, í augnablikinu al momento ちょうど今 바로 지금 dabar, šiuo metu šobrīd, patlaban pada masa ini op het ogenblik for øyeblikket w tej chwili, obecnie په همدى شيبه كښى neste momento pentru mo­ment в настоящее время , в данную минуту práve teraz trenutno u ovom trenutku för ögonblicket, för tillfället ในขณะนี้ şu anda , şimdi 此刻 в данний момент اب ، اس دم vào thời điểm này 此刻 the moment (that)

 exactly when.

I want to see him the moment he arrives.

sodra حالَما، تماماً عندَما، في اللحْظَه моментът no momento em que hned jak genau dann (wenn) i det øjeblik μόλις en cuanto kohe kui در زمان heti kun dès que בַּרֶגָע तुरंत क्षणों में istog trena abban a pillanatban, amint tepat ketika um leið, strax (og) appena , quando ～するとすぐ ...하자마자 kai tik tiklīdz; tai pašā brīdī sejurus zodra med én gang , øyeblikkelig natychmiast په هغه وخت كښى، كله چى no momento em que din momentul (în care), imediat ce как только hneď ako takoj ko onog trenutka så snart [som], med detsamma [som] ตอนที่ ...-er ...-mez (hemen) 一…就… в ту ж саму хвилину عین اسی وقت

 chỉ khi 一 ...

就 ... ，这一刻 moment Momentum and Impulse Connection Momentum and Its Conservation - Lesson 1 - The Impulse-Momentum Change Theorem Momentum and Impulse Connection Real-World Applications As mentioned in the previous part of this lesson , momentum is a commonly used term in sports. When a sports announcer says that a team has the momentum they mean that the team is really on the move and is going to be hard to stop. The term momentum is a physics concept. Any object with momentum is going to be hard to stop. To stop such an object, it is necessary to apply a force against its motion for a given period of time. The more momentum that an object has, the harder that it is to stop. Thus, it would require a greater amount of force or a longer amount of time or both to bring such an object to a halt. As the force acts upon the object for a given amount of time, the object's velocity is changed; and hence, the object's momentum is changed. The concepts in the above paragraph should not seem like abstract information to you. You have observed this a number of times if you have watched the sport of football.

In football, the defensive players apply a force for a given amount of time to stop the momentum of the offensive player who has the ball. You have also experienced this a multitude of times while driving. As you bring your car to a halt when approaching a stop sign or stoplight, the brakes serve to apply a force to the car for a given amount of time to change the car's momentum. An object with momentum can be stopped if a force is applied against it for a given amount of time. A force acting for a given amount of time will change an object's momentum. Put another way, an unbalanced force always accelerates an object - either speeding it up or slowing it down . If the force acts opposite the object's motion, it slows the object down. If a force acts in the same direction as the object's motion, then the force speeds the object up. Either way, a force will change the velocity of an object. And if the velocity of the object is changed, then the momentum of the object is changed. Impulse These concepts are merely an outgrowth of Newton's second law as discussed in an earlier unit.

Newton's second law (Fnet = m • a) stated that the acceleration of an object is directly proportional to the net force acting upon the object and inversely proportional to the mass of the object. When combined with the definition of acceleration (a = change in velocity / time), the following equalities result. F = m • a F = m • ∆v / t If both sides of the above equation are multiplied by the quantity t, a new equation results. F • t = m • ∆v This equation represents one of two primary principles to be used in the analysis of collisions during this unit. To truly understand the equation, it is important to understand its meaning in words. In words, it could be said that the force times the time equals the mass times the change in velocity. In physics, the quantity Force • time is known as impulse. And since the quantity m•v is the momentum, the quantity m•Δv must be the change in momentum. The equation really says that the Impulse = Change in momentum One focus of this unit is to understand the physics of collisions. The physics of collisions are governed by the laws of momentum; and the first law that we discuss in this unit is expressed in the above equation.

The equation is known as the impulse-momentum change equation. The law can be expressed this way: In a collision, an object experiences a force for a specific amount of time that results in a change in momentum. The result of the force acting for the given amount of time is that the object's mass either speeds up or slows down (or changes direction). The impulse experienced by the object equals the change in momentum of the object. In equation form, F • t = m • Δ v. In a collision, objects experience an impulse; the impulse causes and is equal to the change in momentum. Consider a football halfback running down the football field and encountering a collision with a defensive back. The collision would change the halfback's speed and thus his momentum. If the motion was represented by a ticker tape diagram , it might appear as follows: At approximately the tenth dot on the diagram, the collision occurs and lasts for a certain amount of time; in terms of dots, the collision lasts for a time equivalent to approximately nine dots. In the halfback-defensive back collision, the halfback experiences a force that lasts for a certain amount of time to change his momentum.

Since the collision causes the rightward-moving halfback to slow down, the force on the halfback must have been directed leftward. If the halfback experienced a force of 800 N for 0.9 seconds, then we could say that the impulse was 720 N•s. This impulse would cause a momentum change of 720 kg•m/s. In a collision, the impulse experienced by an object is always equal to the momentum change. Representing a Rebounding Collision Now consider a collision of a tennis ball with a wall. Depending on the physical properties of the ball and wall, the speed at which the ball rebounds from the wall upon colliding with it will vary. The diagrams below depict the changes in velocity of the same ball. For each representation (vector diagram, velocity-time graph, and ticker tape pattern), indicate which case (A or B) has the greatest change in velocity, greatest acceleration , greatest momentum change, and greatest impulse . Support each answer. Click the button to check your answer. See Answer a. The velocity change is greatest in case B. In each case the initial velocity is the same. In case B, the object rebounds in the opposite direction with a greater speed than in case A.

This is equivalent to a change from +10 m/s to -5 m/s; whereas, case A has a change from +10 m/s to -2 m/s. b. The acceleration is greatest in case B. Acceleration depends on velocity change and the velocity change is greatest in case B (as stated above) c. The momentum change is greatest in case B. Momentum change depends on velocity change and the velocity change is greatest in case B (as stated above). d. The impulse is greatest in case B. Impulse equals momentum change and the momentum change is greatest in case B (as stated above) Observe that each of the collisions above involve the rebound of a ball off a wall. Observe that the greater the rebound effect, the greater the acceleration, momentum change, and impulse. A rebound is a special type of collision involving a direction change in addition to a speed change. The result of the direction change is a large velocity change. On occasions in a rebound collision, an object will maintain the same or nearly the same speed as it had before the collision. Collisions in which objects rebound with the same speed (and thus, the same momentum and kinetic energy) as they had prior to the collision are known as elastic collisions.

In general, elastic collisions are characterized by a large velocity change, a large momentum change, a large impulse, and a large force. Use the impulse-momentum change principle to fill in the blanks in the following rows of the table. As you do, keep these three major truths in mind: The impulse experienced by an object is the force•time. The momentum change of an object is the mass•velocity change. The impulse equals the momentum change. Click the button to view answers. -4 m/s There are a few observations that can be made in the above table that relate to the computational nature of the impulse-momentum change theorem. First, observe that the answers in the table above reveal that the third and fourth columns are always equal; that is, the impulse is always equal to the momentum change. Observe also that if any two of the first three columns are known, then the remaining column can be computed. This is true because the impulse=force • time. Knowing two of these three quantities allows us to compute the third quantity. And finally, observe that knowing any two of the last three columns allows us to compute the remaining column. This is true since momentum change = mass • velocity change.

There are also a few observations that can be made that relate to the qualitative nature of the impulse-momentum change theorem. An examination of rows 1 and 2 show that force and time are inversely proportional; for the same mass and velocity change, a tenfold increase in the time of impact corresponds to a tenfold decrease in the force of impact. An examination of rows 1 and 3 show that mass and force are directly proportional; for the same time and velocity change, a fivefold increase in the mass corresponds to a fivefold increase in the force required to stop that mass. Finally, an examination of rows 3 and 4 illustrate that mass and velocity change are inversely proportional; for the same force and time, a twofold decrease in the mass corresponds to a twofold increase in the velocity change. We Would Like to Suggest ... Sometimes it isn't enough to just read about it. You have to interact with it! And that's exactly what you do when you use one of The Physics Classroom's Interactives. We would like to suggest that you combine the reading of this page with the use of our Egg Drop Interactive . You can find it in the Physics Interactives section of our website.

The Egg Drop Interactive immerses a learner into a Virtual Egg Drop activity in order to explore the effect of drop height, egg mass, and landing surface upon the outcome of the egg. See Answer The momentum change is the same for each cart. Momentum change equals the impulse; if each cart has the same impulse, then it would follow that they have the same momentum change. 2. In a physics demonstration, two identical balloons (A and B) are propelled across the room on horizontal guide wires. The motion diagrams (depicting the relative position of the balloons at time intervals of 0.05 seconds) for these two balloons are shown below. See Answer Balloon B has the greatest acceleration. The rate at which the velocity changes is greatest for Balloon B; this is shown by the fact that the speed (distance/time) changes most rapidly. See Answer Balloon B has the greatest impulse. Impulse is equal to momentum change. If balloon B has the greatest momentum change, then it must also have the greatest impulse. 3. Two cars of equal mass are traveling down Lake Avenue with equal velocities. They both come to a stop over different lengths of time. The ticker tape patterns for each car are shown on the diagram below.

At what approximate location on the diagram (in terms of dots) does each car begin to experience the impulse? See Answer The collision occurs at approximately the ninth dot (plus or minus a dot). The diagram shows that it is at that location that the cars begin to slow down. See Answer Car A has the greatest acceleration. The velocity change of each car is the same. (They start with the same velocity and each finish with zero velocity.) Yet car A accomplishes this change in less time. Car A accelerates "most rapidly." See Answer The impulse is the same for each car. The impulse equals the momentum change. If the momentum change is the same for each car, then so must be the impulse. 4. The diagram to the right depicts the before- and after-collision speeds of a car that undergoes a head-on-collision with a wall. In Case A, the car bounces off the wall. In Case B, the car crumples up and sticks to the wall. a. In which case (A or B) is the change in velocity the greatest? Explain. See Answer Case A has the greatest velocity change. The velocity change is -9 m/s in case A and only -5 m/s in case B.

See Answer The impulse is greatest for Car A. The impulse equals the momentum change. If the momentum change is greatest for Car A, then so must be the impulse. d. In which case (A or B) is the force that acts upon the car the greatest (assume contact times are the same in both cases)? Explain. See Answer The impulse is greatest for Car A. The force is related to the impulse (I=F*t). The bigger impulse for Car A is attributed to the greater force upon Car A. Recall that the rebound effect is characterized by larger forces; car A is the car which rebounds. 5. Jennifer, who has a mass of 50.0 kg, is riding at 35.0 m/s in her red sports car when she must suddenly slam on the brakes to avoid hitting a deer crossing the road. She strikes the air bag, that brings her body to a stop in 0.500 s. What average force does the seat belt exert on her? Impulse = F*t = 80 N * 0.1 s Impulse = 8 N*s Note that not all the numbers are necessary for computing the impulse; don't "force" the value of mass into the computation.

7. If a 5-kg object experiences a 10-N force for a duration of 0.10-second, then what is the momentum change of the object? Momentum Change = 1.0 kg*m/s The momentum change = mass*velocity change. But since velocity change is not known another strategy must be used to find the momentum change. The strategy involves first finding the impulse (F*t = 1.0 N*s). Since impulse = momentum change, the answer is 1.0 N*s. Forces & Motion - Principle of Moments - Pass My Exams: Easy exam revision notes for GSCE Physics Home > GCSE Physics > Forces & Motion Moment The turning effect of a force is known as the moment. It is the product of the force multiplied by the perpendicular distance from the line of action of the force to the pivot or point where the object will turn. When undoing a nut fastened to a screw by hand one realises that the amount of force required is a lot greater than when undoing the same nut using a spanner. The spanner increases the distance between the fulcrum and the line of action of the force, thus for the same force a greater moment is obtained.

SMALL MOMENT The distance from the fulcrum to the line of action of force is large Principle of Moments The principle of moments states that when in equilibrium the total sum of the anti clockwise moment is equal to the total sum of the clockwise moment. When a system is stable or balance it is said to be in equilibrium as all the forces acting on the system cancel each other out. In equilibrium Total Anticlockwise Moment = Total Clockwise Moment This principle can be explained by considering two people on a seesaw. Moments Acting On A Seesaw Both people exert a downward force on the seesaw due to their weights. Person A’s weight is trying to turn the seesaw anticlockwise whilst person B’s weight is trying to turn the seesaw clockwise. Person A’s Moment = Force x perpendicular distance from fulcrum 1000 x 1 = 1000 Nm Person B’s Moment = Force x perpendicular distance from fulcrum 500 x 2 = 1000 Nm Persons A’s moment = Persons B’s Moment Anticlockwise moment = Clockwise moment

Question: What is a brief period of time and a turning effect produced by a force?
Answer: Moment