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4:10 p.m. EDT

July 10, 2013

A Century of U.S. Central Banking: Goals, Frameworks, Accountability

Remarks by

Ben S. Bernanke

Chairman

Board of Governors of the Federal Reserve System

at

“The First 100 Years of the Federal Reserve:

The Policy Record, Lessons Learned, and Prospects for the Future”

A conference sponsored by the National Bureau of Economic Research

Cambridge, Massachusetts

July 10, 2013

I’d like to thank the National Bureau of Economic Research for organizing this conference in recognition of the Federal Reserve’s centennial, and I’m glad to have the opportunity to participate. In keeping with the spirit of the conference, my remarks today will take a historical perspective. I will leave discussion of current policy to today’s question-and-answer session and, of course, to my congressional testimony next week.

Today, I’ll discuss the evolution over the past 100 years of three key aspects of Federal Reserve policymaking: the goals of policy, the policy framework, and accountability and communication. The changes over time in these three areas provide a useful perspective, I believe, on how the role and functioning of the Federal Reserve have changed since its founding in 1913, as well as some lessons for the present and for the future. I will pay particular attention to several key episodes of the Fed’s history, all of which have been referred to in various contexts with the adjective “Great” attached to them: the Great Experiment of the Federal Reserve’s founding, the Great Depression, the Great Inflation and subsequent disinflation, the Great Moderation, and the recent Great Recession.

The Great Experiment

In the words of one of the authors of the Federal Reserve Act, Robert Latham Owen, the Federal Reserve was established to “provide a means by which periodic panics which shake the American Republic and do it enormous injury shall be stopped.”1 In short, the original goal of the Great Experiment that was the founding of the Fed was the

1 See Owen (1919, p. 24). The Treasury carried out some central banking functions before the creation of the Federal Reserve. In addition, the United States had experimented with central banking before, with the First and Second Banks of the United States. By 1913, however, it had been about 75 years since the latter institution had ceased fulfilling that purpose. Moreover, the Federal Reserve operated somewhat differently from the prior institutions, and, in that respect, its creation amounted to an experiment.

preservation of financial stability.2 At the time, the standard view of panics was that they were triggered when the needs of business and agriculture for liquid funds outstripped the available supply--as when seasonal plantings or shipments of crops had to be financed, for example--and that panics were further exacerbated by the incentives of banks and private individuals to hoard liquidity during such times.3 The new institution was intended to relieve such strains by providing an “elastic” currency--that is, by providing liquidity as needed to individual member banks through the discount window; commercial banks, in turn, would then be able to accommodate their customers. Interestingly, although congressional advocates hoped the creation of the Fed would help prevent future panics, they did not fully embrace the idea that the Fed should help end ongoing panics by serving as lender of last resort, as had been recommended by the British economist and writer Walter Bagehot.4 Legislators imposed limits on the Federal Reserve’s ability t o lend in response to panics, for example, by denying nonmember banks access to the discount window and by restricting the types of collateral that the Fed could accept.5

The framework that the Federal Reserve employed in its early years to promote financial stability reflected in large measure the influence of the so-called real bills

2 Per a review of the 1929 book Wall Street and Washington in the New York Times, “The Federal Reserve System has from the first necessarily been a great experiment, bound to adjust its general policies to the requirements of such novel and varying situations as should arise in the course of our financial history and which could not possibly be foreseen” (Noyes, 1929).

3 Friedman and Schwartz (1963) describe the debate about the elastic currency. Warburg (1914) discusses hoarding and the panic dynamics that the Federal Reserve was established to prevent.

4 See Willis (1923, p. 1407), Carlson and Wheelock (2012), and Bordo and Wheelock (2013). Bagehot ([1873] 1897) is the source of the classic dictum that a panic should be addressed by the central bank, by lending freely at a penalty rate.

5 The Monetary Control Act of 1980 gave all depository institutions access to the discount window. The collateral acceptable to be pledged to the discount window has been expanded significantly over time; in particular, various pieces of banking legislation in the early 1930s enabled the Federal Reserve to make advances to member banks so long as the loans were “secured to the satisfaction” of the Federal Reserve Bank extending the loan.

doctrine, as well as the fact that the United States was on the gold standard.6 In the framework of the real bills doctrine, the Federal Reserve saw its function as meeting the needs of business for liquidity--consistent with the idea of providing an elastic currency--with the ultimate goal of supporting financial and economic stability.7 When business activity was increasing, the Federal Reserve helped accommodate the need for credit by supplying liquidity to banks; when business was contracting and less credit was needed, the Fed reduced the liquidity in the system.

As I mentioned, the Federal Reserve pursued this approach to policy in the context of the gold standard. Federal Reserve notes were redeemable in gold on demand, and the Fed was required to maintain a gold reserve equal to 40 percent of outstanding notes. However, contrary to the principles of an idealized gold standard, the Federal Reserve often took actions to prevent inflows and outflows of gold from being fully translated into changes in the domestic money supply.8 This practice, together with the size of the U.S. economy, gave the Federal Reserve considerable autonomy in monetary policy and, in particular, allowed the Fed to conduct policy according to the real bills doctrine without much hindrance.

The policy framework of the Fed’s early years has been much criticized in retrospect. Although the gold standard did not appear to have greatly constrained U.S. monetary policy in the years after the Fed’s founding, subsequent research has highlighted the extent to which the international gold standard served to destabilize the

6 See Humphrey (1982) for a discussion of the historical evolution of the real bills doctrine.

7 This interpretation follows from the discussion in the Tenth Annual Report of the Federal Reserve Board (Board of Governors, 1924). Soon after the Federal Reserve was founded, its mission shifted to supporting the war effort and then to managing the unwinding of that support. The year 1923 was thus one of the first in which the Federal Reserve confronted normal peacetime financial conditions, and it took the opportunity to articulate its views on the appropriate conduct of policy in such conditions.

8 The Federal Reserve could undo the effects of gold inflows on the domestic money supply through open market operations, discussed later.

global economy in the late 1920s and early 1930s.9 Likewise, economic historians have pointed out that, under the real bills doctrine, the Fed increased the money supply precisely at those times at which business activity and upward pressures on prices were strongest; that is, monetary policy was procyclical. Thus, the Fed’s actio ns tended to increase rather than decrease the volatility in economic activity and prices.10 During this early period, the new central bank did make an important addition to its menu of policy tools. Initially, the Fed’s main tools were the quantity of i ts lending through the discount window and the interest rate at which it lent, the discount rate. Early on, however, to generate earnings to finance its operations, the Federal Reserve began purchasing government securities in the open market--what came to be known as open market operations. In the early 1920s, Fed officials discovered that these operations affected the supply and cost of bank reserves and, consequently, the terms on which banks extended credit to their customers. Subsequently, of course, open market operations became a principal monetary policy tool, one that allowed the Fed to interact with the broader financial markets, not only with banks.11

I’ve discussed the original mandate and early policy framework of the Fed. What about its accountability to the public? As this audience knows, when the Federal Reserve was established, the question of whether it should be a private or a public institution was highly contentious. The compromise solution created a hybrid Federal Reserve System. The System was headed by a governmentally appointed Board, which initially included the Secretary of the Treasury and the Comptroller of the Currency. But the 12 regional Reserve Banks were placed under a mixture of public and private oversight, including

9 See, for example, Eichengreen (1992).

10 See Friedman and Schwartz (1963), Humphrey (1982), and Meltzer (2003).

11 See Strong (1926).

board members drawn from the private sector, and they were given considerable scope to make policy decisions that applied to their own Districts. For example, Reserve Banks were permitted to set their own discount rates, subject to a minimum set by the Board.

While the founders of the Federal Reserve hoped that this new institution would provide financial and hence economic stability, the policy framework and the institutional structure would prove inadequate to the challenges the Fed would soon face.

The Great Depression

The Great Depression was the Federal Reserve’s most difficult test. Tragi cally, the Fed failed to meet its mandate to maintain financial stability. In particular, although the Fed provided substantial liquidity to the financial system following the 1929 stock market crash, its response to the subsequent banking panics was limited at best; the widespread bank failures and the collapse in money and credit that ensued were major sources of the economic downturn.12Bagehot’s dictum to lend freely at a penalty rate in the face of panic appeared to have few adherents at the Federal Reserve of that era.13 Economists have also identified a number of instances from the late 1920s to the early 1930s when Federal Reserve officials, in the face of the sharp economic contraction and financial upheaval, either tightened monetary policy or chose inaction. Some historians trace these policy mistakes to the early death of Benjamin Strong, governor of the Federal Reserve Bank of New York, in 1928, which left the decentralized system without an effective leader.14 Whether valid or not, this hypothesis raises the interesting question of what intellectual framework an effective leader would have drawn on at the

12 See Friedman and Schwartz (1963).

13 Meltzer (2003, pp. 282, 729-30) notes that Board members discussed Bagehot’s ideas but nevertheless did not integrate them fully into their approach to policy.

14 See Friedman and Schwartz (1963, chapter 7).

time to develop and justify a more activist monetary policy. The degree to which the gold standard actually constrained U.S. monetary policy during the early 1930s is debated; but the gold standard philosophy clearly did not encourage the sort of highly expansionary policies that were needed.15 The same can be said for the real bills doctrine, which apparently led policymakers to conclude, on the basis of low nominal interest rates and low borrowings from the Fed, that monetary policy was appropriately supportive and that further actions would be fruitless.16 Historians have also noted the prevalence at the time of yet another counterproductive doctrine: the so-called liquidationist view, that depressions perform a necessary cleansing function.17 It may be that the Federal Reserve suffered less from lack of leadership in the 1930s than from the lack of an intellectual framework for understanding what was happening and what needed to be done.

The Fed’s inadequate policy frameworks ultimately collapsed under the weight of economic failures, new ideas, and political developments. The international gold standard was abandoned during the 1930s. The real bills doctrine likewise lost prestige after the disaster of the 1930s; for example, the Banking Act of 1935 instructed the Federal Reserve to use open market operations with consideration of “the general credit situation of the country,” not just to focus narrowly on short-term liquidity needs.18 The Congress also expanded the Fed’s ability to provide credit through the discount window,

15 Wicker (1965), Temin (1989), and Eichengreen (1992) suggest that U.S. policymakers felt constrained by the gold standard. In contrast, Hsieh and Romer (2006), as well as Bordo, Choudhri, and Schwartz (2002), focus on the short-lived monetary expansion in 1932 as evidence against the existence of important constraints on the Federal Reserve.

16 See Meltzer (2003) and Romer and Romer (2013).

17 See, for example, DeLong (1990).

18 This language amended section 12A(c) of the Federal Reserve Act.

allowing loans to a broader array of counterparties, secured by a broader variety of collateral.19

The experience of the Great Depression had major ramifications for all three aspects of the Federal Reserve I am discussing here: its goals, its policy framework, and its accountability to the public. With respect to goals, the high unemployment of the Depression--and the fear that high unemployment would return after World War II--elevated the maintenance of full employment as a goal of macroeconomic policy. The Employment Act of 1946 made the promotion of employment a general objective for the federal government. Although the Fed did not have a formal employment goal until the Federal Reserve Reform Act of 1977 codified “maximum employment,” along with “stable prices,” as part of the Fed’s so-called dual mandate, earlier legislation nudged the central bank in that direction.20 For example, legislators described the intent of the Banking Act of 1935 as follows: “To increase the ability of the banking system to promote stability of employment and business, insofar as this is possible within the scope of monetary action and credit administration.”21

The policy framework to support this new approach reflected the development of macroeconomic theories--including the work of Knut Wicksell, Irving Fisher, Ralph Hawtrey, Dennis Robertson, and John Maynard Keynes--that laid the foundations for understanding how monetary policy could affect real activity and employment and help 19 For example, section 10B enhanced the powers of the Federal Reserve to lend to member banks, and sections 13(3) and 13(13) enabled the Federal Reserve to provide short-term credit to a wide range of potential borrowers in specific circumstances.

20 More precisely, the three statutory objectives for monetary policy set forth in the Federal Reserve Reform Act of 1977 are maximum employment, stable prices, and moderate long-term interest rates. The dual mandate refers to the first two goals, and the long-term interest rate goal is viewed as likely to emerge from the macroeconomic environment associated with achievement of the employment and price stability goals (Mishkin, 2007). Thus, the interest rate goal of the Federal Reserve Reform Act can be regarded as subsumed within the dual mandate.

21 See U.S. Congress (1935).

reduce cyclical fluctuations. At the same time, the Federal Reserve became less focused on its original mandate of preserving financial stability, perhaps in part because it felt superseded by the creation during the 1930s of the Federal Deposit Insurance Corporation and the Securities and Exchange Commission, along with other reforms intended to make the financial system more stable.

In the area of governance and accountability to the public, policymakers also recognized the need for reforms to improve the Federal Reserve’s structure and decisionmaking. The Banking Act of 1935 simultaneously bolstered the legal independence of the Federal Reserve and provided for stronger central control by the Federal Reserve Board. In particular, the act created the modern configuration of the Federal Open Market Committee (FOMC), giving the Board the majority of votes on the Committee, while removing the Secretary of the Treasury and the Comptroller of the Currency from the Board. In practice, however, the Treasury continued to have considerable sway over monetary policy after 1933, with one economic historian describing the Fed as “in the back seat.”22 During World War II, the Federal Reserve used its tools to support the war financing efforts. However, even after the war, Federal Reserve policy remained subject to considerable Treasury influence. It was not until the 1951 Accord with the Treasury that the Federal Reserve began to recover genuine independence in setting monetary policy.

The Great Inflation and Disinflation

Once the Federal Reserve regained its policy independence, its goals centered on the price stability and employment objectives laid out in the Employment Act of 1946. In the early postwar decades, the Fed used open market operations and the discount rate to 22 See Meltzer (2003).

influence short-term market interest rates, and the federal funds rate gradually emerged as the preferred operating target. Low and stable inflation was achieved for most of the 1950s and the early 1960s. However, beginning in the mid-1960s, inflation began a long climb upward, partly because policymakers proved to be too optimistic about the economy’s ability to sustain rapid growth without inflation.23

Two mechanisms might have mitigated the damage from that mistaken optimism. First, a stronger policy response to inflation--more like that observed in the 1950s--certainly would have helped.24 Second, Fed policymakers could have reacted to continued high readings on inflation by adopting a more realistic assessment of the economy’s productive potential.25 Instead, policymakers chose to emphasize so-called cost-push and structural factors as sources of inflation and saw wage- and price-setting as having become insensitive to economic slack.26 This perspective, which contrasted sharply with Milton Friedman’s famous dictum that “inflation is always and everywhere a monetary phenomenon,” led to Fed support for measures such as wage and price controls rather than monetary solutions to address inflation.27 A further obstacle was the view among many economists that the gains from low inflation did not justify the costs of achieving it.28

The consequence of the monetary framework of the 1970s was two bouts of double-digit inflation. Moreover, by the end of the decade, lack of commitment to

23 See, for example, Orphanides (2003) and Meltzer (2009a).

24 See Romer and Romer (2002b).

25See Lars Svensson’s remarks in S tokey (2002, p. 63).

26 See, for example, Poole (1979), Romer and Romer (2002a, 2013), Bernanke (2004), and Nelson (2005).

27 Estimates of the response of the federal funds rate to inflation for the 1970s generally show only a weak reaction. See Judd and Rudebusch (1998); Taylor (1999a); and Clarida, Galí, and Gertler (2000). For the quotation, see Friedman (1963, p.17).

28 See DeLong (1997) and Taylor (1997) for a discussion of views during the 1970s on the costs of inflation.

controlling inflation had clearly resulted in inflation expectations becoming “unanchored,” with high estimates of trend inflation embedded in longer-term interest rates.

As you know, under the leadership of Chairman Paul Volcker, the Federal Reserve in 1979 fundamentally changed its approach to the issue of ensuring price stability. This change involved an important rethinking on the part of policymakers. By the end of the 1970s, Federal Reserve officials increasingly accepted the view that inflation is a monetary phenomenon, at least in the medium and longer term; they became more alert to the risks of excessive optimism about the economy’s potential output; and they placed renewed emphasis on the distinction between real--that is, inflation-adjusted--and nominal interest rates.29 The change in policy framework was initially tied to a change in operating procedures that put greater focus on growth in bank reserves, but the critical change--the willingness to respond more vigorously to inflation--endured even after the Federal Reserve resumed its traditional use of the federal funds rate as the policy instrument.30 The new regime also reflected an improved understanding of the importance of providing a firm anchor, secured by the credibility of the central bank, for the private sector’s inflation expectations.31 Finally, it entailed a changed view about the

29 For discussion of these points, see Meltzer (2009b).

30 See, for example, Axilrod (1982).

31Central banks’ emphasis on expectations management partly reflected lessons from the rational expectations literature of the 1970s. Monetary policy implications of the rational expectations literature were further clarified by later research. For example, Sargent (1982) brought out dramatically the dependence of inflation expectations on the monetary policy regime in his study of major disinflations, while rational expectations models were extended to include sticky prices (Fischer, 1977; Taylor, 1980; Rotemberg, 1982; Calvo, 1983) and interest rate rules (Sargent and Wallace, 1975; McCallum, 1981; Taylor, 1993, 1999b; Woodford, 2003).

dual mandate, in which policymakers regarded achievement of price stability as helping to provide the conditions necessary for sustained maximum employment.32

The Great Moderation

Volcker’s successful battle a gainst inflation set the stage for the so-called Great Moderation of 1984 to 2007, during which the Fed enjoyed considerable success in achieving both objectives of its dual mandate. Financial stability remained a goal, of course. The Federal Reserve monitored threats to financial stability and responded when the financial system was upset by events such as the 1987 stock market crash and the terrorist attacks of 2001. More routinely, it shared supervisory duties with other banking agencies. Nevertheless, for the most part, financial stability did not figure prominently in monetary policy discussions during these years. In retrospect, it is clear that macroeconomists--both inside and outside central banks--relied too heavily during that period on variants of the so-called Modigliani-Miller theorem, an implication of which is that the details of the structure of the financial system can be ignored when analyzing the behavior of the broader economy.

An important development of the Great Moderation was the increasing emphasis that central banks around the world put on communication and transparency, as economists and policymakers reached consensus on the value of communication in attaining monetary policy objectives.33 Federal Reserve officials, like those at other central banks, had traditionally been highly guarded in their public pronouncements. They believed, for example, that the ability to take markets by surprise was important for

32 See Lindsey, Orphanides, and Rasche (2005).

33 See Woodford (2005). Many of these principles were codified in the emerging doctrine of inflation targeting, the practice of which was greatly advanced by central banks in other countries. One of the most notable examples is New Zealand’s introduction of inflation targeting in 1990.

influencing financial conditions.34 Thus, although Fed policymakers of the 1980s and early 1990s had become somewhat more explicit about policy objectives and strategy, the same degree of transparency was not forthcoming on monetary policy decisions and operations.35 The release of a postmeeting statement by the FOMC, a practice that began in 1994, was, therefore, an important watershed. Over time, the statement was expanded to include more detailed information about the reason for the policy decision and an indication of the balance of risks.36

In addition to improving the effectiveness of monetary policy, these developments in communications also enhanced the public accountability of the Federal Reserve. Accountability is, of course, essential for policy independence in a democracy. During this period, economists found considerable evidence that central banks that are afforded policy independence in the pursuit of their mandated objectives deliver better economic outcomes.37

One cannot look back at the Great Moderation today without asking whether the sustained economic stability of the period somehow promoted the excessive risk-taking that followed. The idea that this long period of calm lulled investors, financial firms, and financial regulators into paying insufficient attention to building risks must have some truth in it. I don’t think we should conclude, though, that we therefore should not strive to achieve economic stability. Rather, the right conclusion is that, even in (or perhaps, especially in) stable and prosperous times, monetary policymakers and financial

34 See, for example, Goodfriend (1986) and Cukierman and Meltzer (1986).

35See Orphanides (2006) for a discussion of the Federal Reserve’s move during the 1980s and 1990s to increased clarity about policy objectives.

36 See Lindsey (2003).

37 See Alesina and Summers (1993) and Debelle and Fischer (1994).

regulators should regard safeguarding financial stability to be of equal importance as--indeed, a necessary prerequisite for--maintaining macroeconomic stability.

Macroeconomists and historians will continue to debate the sources of the remarkable economic performance during the Great Moderation.38 My own view is that the improvements in the monetary policy framework and in monetary policy communication, including, of course, the better management of inflation and the anchoring of inflation expectations, were important reasons for that strong performance. However, we have learned in recent years that while well-managed monetary policy may be necessary for economic stability, it is not sufficient.

The Financial Crisis, the Great Recession, and Today

It has been about six years since the first signs of the financial crisis appeared in the United States, and we are still working to achieve a full recovery from its effects. What lessons should we take for the future from this experience, particularly in the context of a century of Federal Reserve history?

The financial crisis and the ensuing Great Recession reminded us of a lesson that we learned both in the 19th century and during the Depression but had forgotten to some extent, which is that severe financial instability can do grave damage to the broader economy. The implication is that a central bank must take into account risks to financial stability if it is to help achieve good macroeconomic performance. Today, the Federal Reserve sees its responsibilities for the maintenance of financial stability as coequal with its responsibilities for the management of monetary policy, and we have made substantial

38 For a sampling of the debate, see Stock and Watson (2003); Ahmed, Levin, and Wilson (2004); Dynan, Elmendorf, and Sichel (2006); and Davis and Kahn (2008).

institutional changes in recognition of this change in goals. In a sense, we have come full circle, back to the original goal of the Federal Reserve of preventing financial panics.39 How should a central bank enhance financial stability? One means is by assuming the lender-of-last-resort function that Bagehot understood and described

140 years ago, under which the central bank uses its power to provide liquidity to ease market conditions during periods of panic or incipient panic. The Fed’s many liquidity programs played a central role in containing the crisis of 2008 to 2009. However, putting out the fire is not enough; it is also important to foster a financial system that is sufficiently resilient to withstand large financial shocks. Toward that end, the Federal Reserve, together with other regulatory agencies and the Financial Stability Oversight Council, is actively engaged in monitoring financial developments and working to strengthen financial institutions and markets. The reliance on stronger regulation is informed by the success of New Deal regulatory reforms, but current reform efforts go even further by working to identify and defuse risks not only to individual firms but to the financial system as a whole, an approach known as macroprudential regulation.

Financial stability is also linked to monetary policy, though these links are not yet fully understood. Here the Fed’s evolving strategy is to make monitoring, supervision, and regulation the first line of defense against systemic risks; to the extent that risks remain, however, the FOMC strives to incorporate these risks in the cost-benefit analysis applied to all monetary policy actions.40

What about the monetary policy framework? In general, the Federal Reserve’s policy framework inherits many of the elements put in place during the Great

39 See Bernanke (2011).

40 See Bernanke (2002).

Moderation. These features include the emphasis on preserving the Fed’s inflation credibility, which is critical for anchoring inflation expectations, and a balanced approach in pursuing both parts of the Fed’s dual mandate in the medium term. We have also continued to increase the transparency of monetary policy. For example, the Committee’s communications framework now includes a statement of its longer-run goals and monetary policy strategy.41 In that statement, the Committee indicated that it judged that inflation at a rate of 2 percent (as measured by the annual change in the price index for personal consumption expenditures) is most consistent over the longer run with the FOMC’s dual mandate. FOMC participants also regularly provide estimates of the longer-run normal rate of unemployment; those estimates currently have a central tendency of 5.2 to 6.0 percent. By helping to anchor longer-term expectations, this transparency gives the Federal Reserve greater flexibility to respond to short-run developments. This framework, which combines short-run policy flexibility with the discipline provided by the announced targets, has been described as constrained discretion.42 Other communication innovations include early publication of the minutes of FOMC meetings and quarterly postmeeting press conferences by the Chairman.

The framework for implementing monetary policy has evolved further in recent years, reflecting both advances in economic thinking and a changing policy environment. Notably, following the ideas of Lars Svensson and others, the FOMC has moved toward a framework that ties policy settings more directly to the economic outlook, a so-called forecast-based approach.43 In particular, the FOMC has released more detailed

41 The statement can be found at https://www.doczj.com/doc/a41984120.html,/newsevents/press/monetary/20120125c.htm.

42 See Bernanke and Mishkin (1997).

43 In a forecast-based approach, monetary policymakers inform the public of their medium-term targets--say, a specific value for the inflation rate--and attempt to vary the instruments of policy as needed to meet

statements following its meetings that have related the outlook for policy to prospective economic developments and has introduced regular summaries of the individual economic projections of FOMC participants (including for the target federal funds rate). The provision of additional information about policy plans has helped Fed policymakers deal with the constraint posed by the effective lower bound on short-term interest rates; in particular, by offering guidance about how policy will respond to economic developments, the Committee has been able to increase policy accommodation, even when the short-term interest rate is near zero and cannot be meaningfully reduced further.44 The Committee has also sought to influence interest rates further out on the yield curve, notably through its securities purchases. Other central banks in advanced economies, also confronted with the effective lower bound on short-term interest rates, have taken similar measures.

In short, the recent crisis has underscored the need both to strengthen our monetary policy and financial stability frameworks and to better integrate the two. We have made progress on both counts, but more needs to be done. In particular, the complementarities among regulatory and supervisory policies (including macroprudential policy), lender-of-last-resort policy, and standard monetary policy are increasingly evident. Both research and experience are needed to help the Fed and other central banks develop comprehensive frameworks that incorporate all of these elements. The broader conclusion is what might be described as the overriding lesson of the Federal Reserve’s history: that central banking doctrine and practice are never static. We and other central

that target over time. In contrast, an instrument-based approach involves providing the public information about how the monetary policy committee plans to vary its policy instrument--typically, a short-term interest rate, like the federal funds rate--in response to economic conditions. See Svensson (2003).

44 See Yellen (2012) for an elaboration of this point.

banks around the world will have to continue to work hard to adapt to events, new ideas, and changes in the economic and financial environment.

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Journal of Monetary Economics, vol. 53 (January), pp. 123-50. Eichengreen, Barry (1992). Golden Fetters: The Gold Standard and the Great Depression, 1919-1939. New York: Oxford University Press.

【高中】2017人教版高中物理必修一第一章运动的描述单元检测

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高一物理第一章《运动的描述》单元测试试题A卷

高一物理单元测试试题 第一章运动的描述 时间40分钟,赋分100分 一、本题共10小题,每小题4分,共40分.在每小题给出的四个选项中,有的小题只有一个选项正 确,有的小题有多个选项正确.全部选对的得4分,选不全的得2分,有选错或不答的得0分. 1.某校高一的新同学分别乘两辆汽车去市公园游玩。两辆汽车在平直公路上运动,甲车内一同学看见乙车没有运动,而乙车内一同学看见路旁的树木向西移动。如果以地面为参考系,那么,上述观察说明 A.甲车不动,乙车向东运动B.乙车不动,甲车向东运动 C.甲车向西运动,乙车向东运动D.甲、乙两车以相同的速度都向东运动 2.下列关于质点的说法中,正确的是 A.质点是一个理想化模型,实际上并不存在,所以,引入这个概念没有多大意义 B.只有体积很小的物体才能看作质点 C.凡轻小的物体,皆可看作质点 D.如果物体的形状和大小对所研究的问题属于无关或次要因素时,即可把物体看作质点 3.某人沿着半径为R的水平圆周跑道跑了1.75圈时,他的 A.路程和位移的大小均为3.5πR B.路程和位移的大小均为2R C.路程为3.5πR、位移的大小为2R D.路程为0.5πR、位移的大小为2R 4.甲、乙两小分队进行军事演习,指挥部通过现代通信设备,在屏幕上观察到两小分队的具体行军路线如图所示,两小分队同时同地由O点出发,最后同时到达A点,下列说法中正确的是 A.小分队行军路程s甲>s乙 B.小分队平均速度v甲>v乙 C.y-x图象表示的是速率v-t图象 D.y-x图象表示的是位移s-t图象 5.某中学正在举行班级对抗赛,张明明同学是短跑运动员,在百米竞赛中,测得他在5 s末的速度为10.4 m/s,10 s末到达终点的速度为10.2 m/s,则他在全程中的平均速度为 A.10.4 m/s B.10.3 m/s C.10.2 m/s D.10m/s 6.下面的几个速度中表示平均速度的是 A.子弹射出枪口的速度是800 m/s,以790 m/s的速度击中目标

第一章运动的描述单元测试题及答案

第一章《运动的描述》单元测试题及答案. 运动的描述单元测试题 一、单项选择题。是质点的中,不能看作下1.列物体

)( 计算从北京开往广州的的火车途中所用的时、A 间研究绕地球飞行的航天飞机相对地球的飞行、B 周期时,、沿地面翻滚前进的体操运动员C 比较两辆行驶中的车的快慢D、是正,确的中描系参关下2.列于考的述)( A、参考系必须是和地面连在一起的物体、被研究的物体必须沿与参考系的连线运动B 参考系必须是正在做匀速直线运动的物体

或、C 是相对于地面静止的物体、参考系 是为了研究物体的运动而假定D A为不动的 那个物体B的半圆弧3.如右图,某一物体 沿两个半径为R C ,则它的位移和路程分别 C运动到由A 是 2 ( ) A、0,0 B、4 R向下, πR C、4πR向下、4R D、4R向下,2 πR

4.氢气球升到离地面80m的高空时从上面掉落下一物体,物体又上升了10m后开始下落,若取 向上为正,则物体从掉落开始至最终落在地面时的位移和经过的路程分别为 () A、80m,100m B、-80m,100m C、80m,100 m D、-90 m,180 m 5.下列关于平均速度和瞬时速度的说法中

正确的是 () A、做变速运动的物体在相同时间间隔里的平均速度是相同的 B、瞬时速度就是运动的物体在一段较短的时间内的平均速度 C、平均速度就是初末时刻瞬时速度的平均值 D、某物体在某段时间里的瞬时速度都为零,则该物体在这段时间内静止 是的确正,法说的度速加于关列下 6.( ) A、物体的速度越大,加速度也就越大 B、物体的速度为零,加速度也一定为零 3 C、物体的加速度大小等于速度的变化量与时间的比值 D、物体的加速度的方向和速度的方向总是一致

第一章运动的描述

第一篇力学基础 第一章运动的描述 教学时间:5学时 本章教学目标:理解运动的绝对性和相对性;理解位置矢量和位移的不同含义;能够根据运动方程求速度和加速度,能够根据速度和加速度求运动方程的表达式;掌握伽利略变换公式,能够根据相对运动公式解决相关问题。 教学方式:讲授法、讨论法等 教学重点:能够根据运动方程求速度和加速度,能够根据速度和加速度求运动方程的表达式。 在经典力学中,通常将力学分为运动学、动力学和静力学。本章只研究运动学规律。运动学是从几何的观点来描述物体的运动,即研究物体的空间位置随时间的变化关系,不涉及引发物体运动和改变运动状态的原因。 §1.1 参考系坐标系物理模型 一、运动的绝对性和相对性 运动是物质的固有属性。从这种意义上讲,运动是绝对的。 但我们所讨论的运动,还不是这种哲学意义上的广义运动。 即使以机械运动形式而言,任何物体在任何时刻都在不停地运动着。例如,地球就在自转的同时绕太阳公转,太阳又相对于银河系中心以大约250 km/s。的速率运动,而我们所处的银河系又相对于其他银河系大约以600 km/s。的速率运动着。总之,绝对不运动的物体是不存在的。 然而运动又是相对的。

因为我们所研究的物体的运动,都是在一定的环境和特定的条件下运动。例如,当我们说一列火车开动了,这显然是指火车相对于地球(即车站)而言的因此离开特定的环境、特定的条件谈论运动没有任何意义正如恩格斯所说:“单个物体的运动是不存在的——只有在相对的意义下才可以谈运动。” 二、参考系 运动是绝对的,但运动的描述却是相对的因此,在确定研究对象的位置时,必须先选定一个标准物体(或相对静止的几个物体)作为基准;那么这个被选作标准的物体或物体群,就称为参考系。 同一物体的运动,由于我们所选参考系不同,对其运动的描述就会不同。 从运动学的角度讲,参考系的选择是任意的,通常以对问题的研究最方便最简单为原则。研究地球上物体的运动,在大多数情况下,以地球为参考系最为方便(以后如不作特别说明,研究地面上物体的运动,都是以地球为参考系)但是。当我们在地球上发射人造“宇宙小天体”时,则应以太阳为参考系。 三、坐标系 要想定量地描述物体的运动,就必须在参考系上建立适当的坐标系。 在力学中常用的有直角坐标系。根据需要,我们也可选用极坐标系、自然坐标系、球面坐标系或柱面坐标系等。 总的说来,当参考系选定后,无论选择何种坐标系,物体的运动性质都不会改变。然而,坐标系选择得当,可使计算简化。 四、物理模型 任何一个真实的物理过程都是极其复杂的。为了寻找过程中最本质、最基本的规律,我们总是根据所提问题(或所要回答的问题),对真实过程进行理想化的简化,然后经过抽象提出一个可供数学描述的物理模型 现在我们所提的问题是确定物体在空间的位置。若物体的线度比它运动的空间范围小很多时,例如绕太阳公转的地球和调度室中铁路运行图上的列车等;或当物

第一章 运动的描述单元测试(含答案)

《运动的描述》单元测试 一.选择题(每题4分,共36分有的小题只有一个答案正确,有的小题有多个答案正确)1.“小小竹排江中游,巍巍青山两岸走。”这两句诗描述的运动的参考系分别是() A.竹排,流水 B.流水,青山 C.青山,河岸 D.河岸,竹排 2.以下几种关于质点的说法,你认为正确的是() A.只有体积很小或质量很小的物体才可发看作质点 B.只要物体运动得不是很快,物体就可以看作质点 C.质点是一种特殊的实际物体D.物体的大小和形状在所研究的问题中起的作用很小,可以忽略不计时,我们就可以把物体看作质点 3.下列说法正确的是() A.“北京时间10点整”,指的是时间,一节课是40min,指的是时刻 B.列车在上海站停了20min,指的是时间 C.在有些情况下,时间就是时刻,时刻就是时间 D.电台报时时说:“现在是北京时间8点整”,这里实际上指的是时刻 4.短跑运动员在100m竞赛中,测得75m速度为9m/s,10s末到达终点时速度为10.2m/s,则运动员在全程中的平均速度为() A . 9 m/s B . 9.6 m/s C . 10 m/s D. 10.2 m/s 5.下列说法中,正确的是() A.质点做直线运动时,其位移的大小和路程一定相等 B.质点做曲线运动时,某段时间内位移的大小一定小于路程 C.两个位移相同的质点,它们所通过的路程一定相等 D .两个质点通过相同的路程,它们的位移大小一定相等 6.氢氢气球升到离地面80m的高空时从上面掉落下一物体,物体又上升了10m后开始下落,若取向上为正,则物体从掉落开始至地面时位移和经过的路程分别为() A.80m,100m B.-80m,100m C.80m,100 m D.-90 m,180 m 7.如图所示为同一打点计时器在四条水平运动的纸带上打出的点,其中a , b间的平均速度最大的是哪一条? 8.以下关于加速度的说法中,正确的是: A.加速度为0的物体一定处于静止状态 B.物体的加速度减小,其速度必随之减小C.物体的加速度增加,其速度不一定增大 D.物体的加速度越大,其速度变化越快9. 关于速度,速度改变量,加速度,正确的说法是: A.物体运动的速度改变量很大,它的加速度一定很大 B.速度很大的物体,其加速度可以很小,可以为零 C.某时刻物体的速度为零,其加速度不可能为零 D.加速度很大时,运动物体的速度一定很大

第一章运动的描述

第一章运动的描述 【本章阅读材料】 一.参考系 1.定义:在描述一个物体的运动时,选来作为标准的假定不动的物体,叫做参考系。 2.对同一运动,取不同的参考系,观察的结果可能不同。 3.运动学中的同一公式中涉及的各物理量应以同一参考系为标准,如果没有特别指明,都是取地面为参考系。 二.质点 1.定义:质点是指有质量而不考虑大小和形状的物体。 2.质点是物理学中一个理想化模型,能否将物体看作质点,取决于所研究的具体问题,而不是取决于这一物体的大小、形状及质量,只有当所研究物体的大小和形状对所研究的问题没有影响或影响很小,可以将其形状和大小忽略时,才能将物体看作质点。 三.时间与时刻 1.时刻:指某一瞬时,在时间轴上表示为某一点。 2.时间:指两个时刻之间的间隔,在时间轴上表示为两点间线段的长度。 3.时刻与物体运动过程中的某一位置相对应,时间与物体运动过程中的位移(或路程)相对应。 四.位移和路程 1.位移:表示物体位置的变化,是一个矢量,物体的位移是指从初位置到末位置的有向线段,其大小就是此线段的长度,方向从初位置指向末位置。 2.路程:路程等于运动轨迹的长度,是一个标量。 当物体做单向直线运动时,位移的大小等于路程。 五.速度、平均速度、瞬时速度 1.速度:是表示质点运动快慢的物理量,在匀速直线运动中它等于位移与发生这段位移所用时间的比值,速度是矢量,它的方向就是物体运动的方向。

2.平均速度:物体所发生的位移跟发生这一位移所用时间的比值叫这段时间内的平均速度,即t v x =,平均速度是矢量,其方向就是相应位移的方向。仅能粗略描述物体的运动的快慢程度。 3.瞬时速度:运动物体经过某一时刻(或某一位置)的速度,其方向就是物体经过某有一位置时的运动方向。大小称之为速率。 它能精确描述物体运动的快慢程度。 (4)极短时间内的平均速度等于某时刻的瞬时速度。 六.加速度 1.加速度是描述物体速度变化快慢的的物理量,是一个矢量,方向与速度变化的方向相同。 2.做匀变速直线运动的物体,速度的变化量与发生这一变化所需时间的比值叫加速度,即t v v t v a 0-=??= 3.对加速度的理解要点: (1)加速度的大小和速度无直接关系。质点的运动的速度大,加速度 不一定大;速度小,其加速度不一定小;速度为零,其加速度不一定为零; (2)加速度的方向不一定和速度方向相同。质点做加速直线运动时,加速度与速度方向相同;质点做减速直线运动时,加速度与速度方向相反; (3)物体做加速直线运动还是做减速直线运动,判断的依据是加速度的方向和速度方向是相同还是相反,只要加速度方向跟速度方向相同,物体的速度一定增大(即加速直线运动),只要加速度方向跟速度方向相反,物体的速度一定减小(即减速直线运动)。

第1章运动的描述章末检测

第一章运动的描述 (时间:90分钟满分:100分) 一、选择题(本题共10小题,每小题4分,共40分) 1.2008年9月25日晚21点10分,在九泉卫星发射中心将我国自行研制的“神舟”七号载人航天飞船成功地送上太空,飞船绕地球飞行一圈时间为90分钟,则() A.“21点10分”和“90分钟”前者表示“时刻”后者表示“时间” B.飞船绕地球飞行一圈,它的位移和路程都为0 C.飞船绕地球飞行一圈平均速度为0,但它在每一时刻的瞬时速度都不为0 D.地面卫星控制中心在对飞船进行飞行姿态调整时可以将飞船看成质点 2.明代诗人曾写下这样一首诗:“空手把锄头,步行骑水牛;人在桥上走,桥流水不流.”其“桥流水不流”中的“桥流”应理解成其选择的参考系是() A.水B.桥C.人D.地面 3.物体沿一直线运动,下列说法中正确的是() A.物体在第一秒末的速度是5 m/s,则物体在第一秒内的位移一定是5 m B.物体在第一秒内的平均速度是5 m/s,则物体在第一秒内的位移一定是5 m C.物体在某段时间内的平均速度是5 m/s,则物体在每一秒内的位移都是5 m D.物体在某段位移内的平均速度是5 m/s,则物体在经过这段位移一半时的速度一定是5 m/s 4.甲、乙两个物体在同一直线上运动(始终没有相遇),当规定向东为正方向时,它们的加速度分别为a甲=4 m/s2,a乙=-4 m/s2.下列对甲、乙两物体运动情况的判断中,正确的是() A.甲的加速度大于乙的加速度 B.甲、乙两物体的运动方向一定相反 C.甲的加速度方向和速度方向一致,乙的加速度方向和速度方向相反 D.甲、乙两物体的速度都有可能越来越大 5.一辆汽车从静止开始由甲地出发,沿平直公路开往乙地,汽车先做匀加速运动.接着做匀减速运动,到达乙地刚好停止,其速度图象如图1所示,那么在0~t0和t0~3t0两段时间内() 图1 A.加速度大小之比为2∶1,且方向相反 B.位移大小之比为1∶2,且方向相反 C.平均速度大小之比为2∶1 D.平均速度大小之比为1∶1 6.物体由静止开始运动,加速度恒定,在第7 s内的初速度是2.6 m/s,则物体的加速度是() A.0.46 m/s2B.0.37 m/s2 C.2.6 m/s2D.0.43 m/s2 7. 图2

第一章运动的描述

第1章 怎样描述物体的运动测评 (时间:45分钟,满分:100分) 一、本题共8小题,每小题5分,共40分不定项选择. 1.如图所示的是体育摄影中“追拍法”的成功之作,摄影师眼中清晰的运动员是静止的,而模糊的背景是运动的,摄影师用自己的方式表达了运动的美.请问摄影师选择的参考系是 A .大地 B .太阳 C .运动员 D .步行的人 2.在下列各种情况中,物体可看做质点的是 A .正在做课间操的同学们都可以看做质点 B .从地面控制中心的屏幕上观察“嫦娥一号”的运动情况 时,“嫦娥一号”可以看做质点 C .观察航空母舰上的舰载飞机起飞时,可以把航空母舰看做质点 D .在作战地图上确定航空母舰的准确位置时,可以把航空母舰看做质点 3.中国飞人刘翔,在2008年5月10日的大阪国际田径大奖赛男子110米栏的比赛中,以13秒19的成绩如愿摘金,在大阪大奖赛上夺得五连冠.关于比赛的下列说法中正确的是 A .110 m 是刘翔比赛中位移的大小 B .13秒19是刘翔夺冠的时刻 C .刘翔比赛中的平均速度约是8.3 m/s D .刘翔经过终点线时的速度一定等于8.3 m/s 4.让一个小球从2 m 高处落下,被地面弹回,在1 m 高处被接住,则小球在这一过程中 A .位移大小是3 m B .位移大小是1 m C .位移大小是2 m D .路程是2 m 5.(2008山东学业水平测试,4)下列事例中有关速度的说法,正确的是 A .汽车速度计上显示80 km/h ,指的是平均速度 B .某高速公路上的限速为110 km/h, 指的是平均速度 C .火车从济南到北京的速度约为220 km/h, 指的是瞬时速度 D .子弹以900 km/h 的速度从枪口射出,指的是瞬时速度 6.下列对加速度的定义式a =Δv Δt 的理解正确的是 A .加速度a 与速度变化量Δv 成正比 B .加速度a 的大小由速度变化量Δv 决定 C .加速度a 的方向与Δv 方向相同 D .加速度a 决定于速度变化率Δv Δt 7.如图所示分别为甲、乙两物体的st 图像,则下列关于甲、乙两物体的速度都正确的是 A .v 甲=30 m/s v 乙=30 m/s B .v 甲=20 m/s v 乙=30 m/s C .v 甲=30 m/s v 乙=20 m/s D .v 甲=45 m/s v 乙=15 m/s 8.甲、乙两个物体在同一直线上运动的vt 图像如图所示,由 图像可知两物体 A .速度方向相同,加速度方向相反 B .速度方向相反,加速度方 向相同 C .甲的加速度大于乙的加速度 D .甲的加速度小于乙的加速度 第Ⅱ卷(非选择题 共60分) 二、实验题:本题15分,把答案填在题中横线上. 9.在研究匀变速直线运动的实验中,一记录小车运动情况的纸带 如图所示,图中A 、B 、C 、D 、E 、F 为相邻的计数点,相邻的计数点 间的时间间隔为T =0.1 s .求: (1)各点的瞬时速度v B =______m/s ,v C =______m/s ,v D =______m/s ,v E =______m/s. (2)打点计时器打A 点开始计时,在下面图中作出小车的vt 图像.

2321中心对称

23.2 .1中心对称(1)教学设计 第一课时 教学内容 两个图形关于这个点对称或中心对称、对称中心、关于中心的对称点等概念及其运用它们解决一些实际问题. 教学目标 了解中心对称、对称中心、关于中心的对称点等概念及掌握这些概念解决一些问题. 复习运用旋转知识作图,?旋转角度变化,?设计出不同的美丽图案来引入旋转180°的特殊旋转──中心对称的概念,并运用它解决一些实际问题. 重难点、关键 1.重点:利用中心对称、对称中心、关于中心对称点的概念解决一些问题. 2.难点与关键:从一般旋转中导入中心对称. 教具、学具准备 小黑板、三角尺 教学过程 一、检查导读单完成情况 1、组长检查自己小组成员的完成情况,然后向老师汇报 2、每个小组派代表对导读单上的问题进行展示、讲解,老师给予评价

二、生成单问题的解决 1、各同学对生成单上的问题进行交流,讨论,作答。(老师在各小组巡视,讲解共同存在的问题) 2、每小组派一名代表在黑板上展示本组老师指定的问题,并讲解本组的解题思路、方法,板书过程。 3、其他小组可以补充,存在问题的指出问题,老师最后指导,进行评价 三、交流本节课的收获 1、各小组畅所欲言,谈本节课的收获、感悟,包括知识、模糊点的澄清、经验的获得、获得成功后的成就感。 2、归纳出本节课的要点。 四、重点的训练、拓展 发放训练单,对重点知识强化训练,个别指导差生,教师组织参与评价,针对共性问题集中指导。 五、教师归纳总结,布置作业。

23.2.1.中心对称(1)问题导读生成单——评价单 班级:组名:姓名: 一.自读课本 1.什么叫旋转?什么叫旋转角? 2. 请同学们独立完成下题. 如图,△ABC绕点O旋转,使点A旋转到 点D处,画出旋转后的三角形,?并写出简要 做法 二、探索新知 问题:作出如图的两个图形绕点O旋转 180°的图案,并回答下列的问题: 1.以O为旋转中心,旋转180°后两个图 形是否重合? 2.各对称点绕O旋转180°后,这三点是否在一条直线上? 像这样, 这个点叫做对称中心. 这两个图形中的对应点叫做关于中心的对称点. 例1.如图,四边形ABCD绕D点旋转180°,请作出旋转后的图案,写出作法并回答. (1)这两个图形是中心对称图形吗?如果是对称中心是哪一点?如果不是,请说明理由. (2)如果是中心对称,那么A、B、C、D关于中心的对称点是哪些点. 例2.如图,已知AD是△ABC的中线,画出以点D为对称中心,与△ABD?成中心对称的三角形. 三、巩固练习:教材P64 练习1.2

1-:第一章 运动的描述(知识框架)

第一章 运动的描述(知识框架) - 1 - 第一章 运动的描述(知识框架) 运 动 的 描 述 质点:形状、大小可忽略不计的有质量的点 物体可看成质点的条件:物体的大小、形状对研究问题的影响可忽略不计 参考系:描述一个物体运动时,用来选作标准的另外的物体 坐标系:用来准确描述物体位置及位置变化 基本概念 概念对比 时刻:是指某一瞬时,在时间轴上是一个点 时间:是时间间隔的简称,指一段持续的时间间隔, 两个时刻的间隔表示时间 路程:质点实际运动的轨迹的长度;单位m 。 位移:从物体运动的起点指向运动的终点的有向线段,表示位置的变化; 单位:m 矢量:既有大小,又有方向的物理量;如:速度、位移 标量:只有大小,没有方向的物理量;如:路程、时间 定义:物体运动的位移与时间的比值 物理意义:表示物体运动的快慢 速度 公式:t x t x =??=ν;单位:m/s 矢量性:矢量 定义:某一过程中的一段位移与其所对应的时间的比值 物理意义:粗略地表示物体运动的快慢 公式:t x t x =? ?= ν ;单位:m/s 矢量性:矢量 平均速度 速率:表示速度的大小;标量。 平均速率:表示某义过程中的一段路程与其所用的时间的比值 是一个标量 速率 速度 定义:速度的变化量与时间的比值 物理意义:表示速度变化的快慢 公式: t v v t v a t 0-=??=; 单位:m/s 2 矢量性:矢量,与速度变化量方向相同 加速度 实验 打点计时器分类:电磁打点计时器和电火花打点计时器 振动频率:均为50Hz ,即每隔0.02s 打一个点 纸带分析:a.可计算物体运动的平均速度 b .粗略计算瞬时速度

人教版高一物理上册 运动的描述检测题(Word版 含答案)

一、第一章运动的描述易错题培优(难) 1.质点做直线运动的v-t 图象如图所示,则() A.3 ~ 4 s 内质点做匀减速直线运动 B.3 s 末质点的速度为零,且运动方向改变 C.0 ~ 2 s 内质点做匀加速直线运动,4 ~ 6 s 内质点做匀减速直线运动,加速度大小均为 2 m/s2 D.6 s内质点发生的位移为 8 m 【答案】BC 【解析】 试题分析:矢量的负号,只表示物体运动的方向,不参与大小的比较,所以3 s~4 s内质点的速度负方向增大,所以做加速运动,A错误,3s质点的速度为零,之后开始向负方向运动,运动方向发生变化,B错误,图线的斜率表示物体运动的加速度,所以0~2 s内质点做匀加速直线运动,4 s~6 s内质点做匀减速直线运动,加速度大小均为2 m/s2,C正确,v-t图像围成的面积表示物体的位移,所以6 s内质点发生的位移为0,D错误, 考点:考查了对v-t图像的理解 点评:做本题的关键是理解v-t图像的斜率表示运动的加速度,围成的面积表示运动的位移,负面积表示负方向位移, 2.如图,直线a和曲线b分别是在平直公路上行驶的汽车a和b的位置一时间(x一t)图线,由图可知 A.在时刻t1,a车追上b车 B.在时刻t2,a、b两车运动方向相反 C.在t1到t2这段时间内,b车的速率先减少后增加 D.在t1到t2这段时间内,b车的速率一直比a车大 【答案】BC 【解析】 【分析】

【详解】 由x—t图象可知,在0-t1时间内,b追a,t1时刻相遇,所以A错误;在时刻t2,b的斜率为负,则b的速度与x方向相反,所以B正确;b图象在最高点的斜率为零,所以速度为零,故b的速度先减小为零,再反向增大,所以C正确,D错误. 3.高速公路上用位移传感器测车速,它的原理如图所示,汽车D向右匀速运动,仪器C 在某一时刻发射超声波脉冲(即持续时间很短的一束超声波),经过时间t1接收到被D反射回来的超声波,过一小段时间后又发射一个超声波脉冲,发出后经过时间t2再次接收到反射回来的信号,已知超声波传播的速度为v0,两次发射超声波脉冲的时间间隔为△t,则下面说法正确的是() A.第一次脉冲测得汽车和仪器C的距离为 01 1 2 v t B.第二次脉冲测得汽车和仪器C的距离为02 v t C.位移传感器在两次测量期间,汽车前进距离为 021 1 () 2 v t t- D.测得汽车前进速度为021 21 () 2 v t t t t t - +?- 【答案】ACD 【解析】 【分析】 【详解】 AB.超声波是匀速运动的,往返时间相同,第一次脉冲测得汽车和仪器C的距离为01 1 2 v t,第二次脉冲测得汽车和仪器C的距离为 02 1 2 v t,故A正确,B错误; C.则两次测量期间,汽车前进的距离为 () 021 1 2 s v t t =- 故C正确; D.超声波两次追上汽车的时间间隔为 12 22 t t t t ' ?=?-+ 故速度

第一章 运动的描述

§1.1 质点、参考系和坐标系 一.机械运动:一个物体相对于另一个物体的位置变化,叫做机械运动(简称运动)。机械运动包括:平动、转动、机械振动。物体的运动轨迹可能是直线也可能是曲 线。 二.质点:一个有质量的点,把实际物体看做一个有质量的点。质点是一个理想化的物 理模型,实际并不存在,是为了方便描述物体的运动将实际物体抽象成一个点。这个点不同于几何点,尽管它们都是零维(零维指没有长、宽、高的维)的,但质点是有质量的,它代表着实际的物体。把一个实际的物体看做质点是抓住了事物的主要矛盾而忽略了次要因素,这也是物理学研究的一种很重要的方法。今后在物理学中经常会用到这种方法。 三.实际物体能被看做质点的条件:实际物体能否被看做质点要看问题本身,同一 个物体在甲问题中能看做质点而在乙问题中就不能看成质点了。具体要注意以下几点:①如果物体的几何形状和尺度对研究问题本身影响很小,以至于可以不考虑物体的形状时可以把物体看做质点。 比如,我们要计算一列火车从北京到上海的时间,因为火车的几何尺度与北京到上海的距离无法比拟,因此我们可以把火车看成质点。 ②作平动的物体一般可以被视为质点,但这也不是绝对的。 比如,火车的运动可以被看做平动,我们要计算一列火车从北京到上海的时间,因为火车的几何尺度与北京到上海的距离无法比拟,因此我们可以把火车看成质点。但是要计算一列火车穿越一个山洞的时间时,就不能把火车看做质点了。 ③作转动的物体一般不能看作质点,但这也不是绝对的。 比如,研究一根绕固定轴转动的木棒的运动情况,就不能把木棒看作质点。但是研究作圆周运动的物体时可以把物体看做质点。 ④并不是很小的物体就一定能视为质点,而很大的物体就不能视为质点。 在高中阶段我们所接触到的物体大部分是可以被视为质点的。 例题: 1.关于运动员和球类能否看成质点,以下说法正确的是() A.研究跳高运动员的起跳和过杆动作时,可以把运动员看成质点 B.研究花样滑冰运动员的冰上动作时,能把运动员看成质点 C.研究足球的射门速度时,可以把足球看成质点 D.研究乒乓球弧圈球的接球时,能把乒乓球看成质点 2.在下列物体的运动中,可把物体视为质点的是() A.研究“神州七号”绕地球运动的圈数时 B.对“神州七号”进行姿态调整时 C.研究跳水运动员在空中的翻滚运动时 D.研究从滑梯上滑下的小孩 四.参考系:为了描述物体的运动,需要先选定一个假定不动的物体作标准,看要描述 的那个物体相对于这个标准物体是如何运动的,这个被选作标准的物体就叫做参考系(参照物)。

人教版必修一第一章《运动的描述》单元教学设计1(精品).doc

第一章运动的描述 (一)全章知识脉络,知识体系 基本概念图解

一、质点、参考系、位移、路程 1.下列物体中,不能看作质点的是() A.计算从北京开往上海的途中,与上海的距离时的火车 B.研究航天飞机相对地球的飞行周期时,绕地球飞行的航天飞机 C.沿地面翻滚前进的体操运动员 D. 比较两辆行驶中的车的快慢 2.下列关于参考系的描述中,正确的是() A.参考系必须是和地面连在一起的物体 B.被研究的物体必须沿与参考系的连线运动 C.参考系必须是正在做匀速直线运动的物体或是相对于地面静止的物体 D.参考系是为了研究物体的运动而假定为不动的那个物体 四、计算题(共27分) 16.(8分)已知一汽车在平直公路上运动,它的位移一时间图象如图(甲)所示. (1)根据图象在图(乙)所示的位置坐标轴上标出A、B、C、D、E各点代表的汽车的位置 (2)求出下列各段时间内汽车的路程和位移大小 ①第 l h内.②前6 h内③前7 h内④前8 h内 17. (9分)A、B、C三地彼此间的距离均为 a,如图所示物体以每秒走完距离a的速度从A点出发,沿折线经B、C点又回到A点试分析说明从运动开始经1 s、2 s、

3 s ,物体的位移大小和路程各为多少? 18.(10分)如图所示为一物体沿直线运动的s-t 图象,根据图象:求 (1)第2 s 内的位移,第4 s 内的位移,前5 s 的总路程和位移 (2)各段的速度 (3)画出对应的v -t 图象 二、速度(瞬时速度、平均速度) 1.试判断下面的几个速度中哪个是瞬时速度 A .子弹出枪口的速度是800 m/s ,以790 m/s 的速度击中目标 B .汽车从甲站行驶到乙站的速度是40 km/h C .汽车通过站牌时的速度是72 km/h D .小球第3s末的速度是6 m/s 2.下列说法中正确的是 A .做匀速直线运动的物体,相等时间内的位移相等 B .做匀速直线运动的物体,任一时刻的瞬时速度都相等 C .任意时间内的平均速度都相等的运动是匀速直线运动 D .如果物体运动的路程跟所需时间的比值是一个恒量,则此运动是匀速直线运动 3.下面关于瞬时速度和平均速度的说法正确的是 A .若物体在某段时间内每时刻的瞬时速度都等于零,则它在这段时间内的平均速度一 定等于零 B .若物体在某段时间内的平均速度等于零,则它在这段时间内任一时刻的瞬时速度一 定等于零 B

高一物理必修一第一章《运动的描述》单元测试题(含详细解答)[1]

《运动的描述》单元测试题 本卷分第Ⅰ卷(选择题)和第Ⅱ卷(非选择题)两部分.满分100分,时间90分钟. 第Ⅰ卷(选择题共40分) 一、选择题(共10小题,每小题4分,共40分,在每小题给出的四个选项中,有的小题只有一个选项符合题目要求,有些小题有多个选项符合题目要求,全部选对的得4分,选不全的得2分,有选错或不答的得0分) 1.下列关于质点的说法正确的是() A.研究和观察日食时,可以把太阳看成质点 B.研究地球的公转时,可以把地球看成质点 C.研究地球的自转时,可以把地球看成质点 D.原子核很小,必须把它看成质点 2.(广东惠阳08-09学年高一上学期期中)2008年9月25日晚21点10分,我国在九泉卫星发射中心将我国自行研制的“神舟7号”宇宙飞船成功地送上太空,飞船绕地球飞行一圈时间为90分钟.则() A.“21点10分”和“90分钟”前者表示“时刻”后者表示“时间” B.卫星绕地球飞行一圈,它的位移和路程都为0 C.卫星绕地球飞行一圈平均速度为0,但它在每一时刻的瞬时速度都不为0 D.地面卫星控制中心在对飞船进行飞行姿态调整时可以将飞船看作质点 3.甲物体以乙物体为参考系是静止的,甲物体以丙物体为参考系又是运动的,那么,以乙物体为参考系,丙物体的运动情况是() A.一定是静止的 B.运动或静止都有可能 C.一定是运动的 D.条件不足,无法判断 . 4.(福建厦门一中09-10学年高一上学期期中)两个人以相同的速率同时从圆形轨道的A点出发,分别沿ABC和ADC行走,如图所示,当他们相遇时不相同的物理量是() A.速度B.位移 C.路程D.速率

5.两个质点甲和乙,同时由同一地点向同一方向做直线运动,它们的v -t 图象如图所示,则下列说法中正确的是( ) A .质点乙静止,质点甲的初速度为零 B .质点乙运动的速度大小、方向不变 C .第2s 末质点甲、乙速度相同 D .第2s 末质点甲、乙相遇 6.某人爬山,从山脚爬上山顶,然后又从原路返回到山脚,上山的平均速率为v 1,下山的平均速率为v 2,则往返的平均速度的大小和平均速率是( ) A.v 1+v 22,v 1+v 22 B.v 1-v 22,v 1-v 2 2 C .0,v 1-v 2 v 1+v 2 D .0,2v 1v 2 v 1+v 2 7.(银川一中09-10学年高一上学期期中)下列关于物体运动的说法,正确的是( ) A .物体速度不为零,其加速度也一定不为零 B .物体具有加速度时,它的速度可能不会改变 C .物体的加速度变大时,速度也一定随之变大 D .物体加速度方向改变时,速度方向可以保持不变 8.下表是四种交通工具的速度改变情况,下列说法正确的是( ) 初始速度(m/s) 经过时间(s) 末速度(m/s) ① 2 3 11 ② 0 3 6 ③ 0 20 6 ④ 100 20 A.①的速度变化最大,加速度最大 B .②的速度变化最慢 C .③的速度变化最快 D .④的末速度最大,但加速度最小

第一章运动的描述

0(90分钟,满分100分) 00一、选择题(本大题有14小题,每小题2分,共28分) 0 1 ?使用刻度尺测长度时,下列说法不正确的是() 0 A.放置刻度尺时,刻度尺应沿所测长度放置,并且必须从零刻度线量起 0 B.刻度尺读数时,视线要与尺面垂直,并要正对刻度线 0 C.读数时,要估读到分度值的下一位 0 D.记录时,要记下测量的数字和单位 0 2、用毫米刻度尺测量工件的长度,将其一端与10cm处的刻度线对准,另外一端0恰好与24 cm的刻度线对齐,次工件的长度记为() 答 B .看台上坐着的观众 A . A 与 B B . A 与 C C . C 与 D D . B 与C 6 (2014?绵阳)汽车站并排停放着两辆大客车,甲车突然相对地面向后行驶,乙车仍相对地面静止,这时乙车上坐在座椅上的乘客却觉得乙车在向前行驶.则该乘客选择的参照物可能是() A.乙车 B.甲车 C.房屋 D.树木 7、下列四个选项中,平均速度最大的是( ) A.航模飞行器以60 m/min的速度匀速飞行100 m B.汽车以40km/h的速度在公路上匀速行驶200 m C.百米赛跑中运动员用12 s跑完全程 D.从30 m高处竖直下落的物体用了2 s 8、甲、乙两车分别从P、Q两点同时同向运动,它们的s--t图像分别如图a,b所示,经过6秒甲乙相遇。甲、乙的速度分别为V甲、V乙,P、Q间的距离为S 则() 9、甲乙两物体从同一地点同时同方向做直线运动,其S---T图像如图所示,由图 像可知() 第一章运动的描述C.地面 D .刘翔前方立着的栏 4、右图是甲、乙两辆同时从同一地点出发的小车的s-t图像,由图像可知( 0 0 0 0 0 0 0 0 0 0 0 0 线 A. 7?20秒钟乙车做匀速直线运动 B .在0?5秒时间内,乙车的速度比甲车的速度大 C .第10秒钟时,甲、乙两车速度相同 D .经过5秒钟,甲车通过的路程比乙车大 5、如图所示的图象中,描述的是同一种运动形式的是( ) S 4 V 4 5 4 v4 B D 两物体衣15 -20-内都嫩匀連逮功■且* ■

第一章 运动的描述(人教版配套精练检测题)

第一章运动的描述 一、选择题 1.在研究下述运动时,能把物体看作质点的是( ) A.研究地球的自转 B.研究乒乓球的旋转 C.研究火车从北京运行到上海 D.研究悬挂的轻绳下系着的小钢球的摆动 2.关于参考系的选择,以下说法中正确的是( ) A.参考系必须选择静止不动的物体 B.任何物体都可以被选作参考系 C.参考系就是不动的物体 D.参考系必须是和地面连在一起的物体 3.下列说法中哪些表示的是时刻( ) A.2008年8月8日晚20∶00,第二十九届奥林匹克运动会在北京开幕 B.校运动会100 m赛跑的最好成绩是12.8 s C.学校早8∶00开始上课 D.人造地球卫星绕地球运行的最小周期是86 min 4.下列关于路程和位移的说法中,正确的是( ) A.位移为零时,路程一定为零 B.路程为零时,位移不一定为零 C.物体沿直线运动时,位移的大小可以等于路程 D.物体沿曲线运动时,位移的大小可以等于路程 5.一个质点在x轴上运动,各个时刻的位置坐标如下表,则此质点开始运动后在 前几秒内位移的大小最大的是( ) A.1 s B.2 s C.3 s D.4 s

6.图示为高速摄影机拍摄到的子弹穿过苹果瞬间的照片。该照片经过放大后分析出,在曝光时间内,子弹影像前后错开的距离约为子弹长度 的1%~2%。已知子弹飞行速度约为500 m/s,因此可 估算出这幅照片的曝光时间最接近( ) A.10-3 s B.10-6 s C.10-9 s D.10-12 s 7.下列说法中正确的是( ) A.变速直线运动的速度是变化的 B.平均速度即为一段时间内初末速度的平均值 C.瞬时速度是物体在某一时刻或在某一位置时的速度 D.瞬时速度可看作时间趋于无穷小时的平均速度 8.下列位移图象中,表示物体始终做匀速直线运动的是( ) A B C D 9.下列关于速度、加速度的描述中,正确的是( ) A.加速度在数值上等于单位时间内速度的变化量 B.物体的速度为零时,加速度也为零 C.物体的速度变化量越大,加速度越大 D.物体的速度变化越快,加速度越大 10.用打点计时器研究物体运动时,接通电源和让纸带随物体开始运动,这两个操作的时间关系应当是( ) A.先接通电源,后释放纸带B.先释放纸带,后接通电源 C.释放纸带的同时接通电源D.先释放纸带或先接通电源都可以 11.如图为某运动物体的速度—时间图象,下列说法中正确的是( ) A.物体以某初速开始运动,在0~2 s内加速运动,2~4 s内匀速运动,4~ 6 s内减速运动 5

高一物理必修1第一章运动的描述知识点总结

第一章运动的描述 第二章第1讲运动的描述 一. 质点 1.定义:在某些情况下,不考虑物体的和,把它简化成一个有的点,称为质点。 2.物体看做质点的条件:物体的和对所研究的问题没有影响时,就可以把物体当作质点。 3.质点是一种的物理模型,是一种科学抽象,实际不存在。 二. 参考系 1 .定义:为了描述物体的,另外选来作为的假定不动的物体,称为参考系。 2.参考系的选取原则上是的,但对同一个物体的运动,选取不同的参考系,观察到的结果可能是的。以研究问题的方便为原则,通常研究地面上的物体一般选为参考系。 三.坐标系 1.定义:在研究物体的运动时,为了定量地描述物体的及,需要在参考系上建立适当的坐标系。 2.根据描述的物体运动的复杂程度,可将坐标系分为、、。 一.时间和时刻 1.时刻:表示物体运动的,时间轴上用表示,对应的是位置、速度等状态量。 2.时间:指两个时刻之间的,时间轴上用表示,对应的是位移、路程等过程 量。 二.路程和位移 1.路程:物体的长度,只有大小,没有方向,是量。 2.位移:表示物体的物理量,用从指向的有向线段表示, 大小只与有关,与物体运动路径无关。既有大小,又有方向,是量。 3.联系:当物体作运动时,路程=位移的大小。

一.平均速度 1.平均速度:与发生这段位移所用的比值,叫做物体在这段时间内的平均速度。 v,平均速度只能(“粗略”“精确”)描述物体运动的快慢,对同即 一运动物体,在不同的过程,它的平均速度可能是的,因此,平均速度必须指明对应的 或。平均速度既有大小,又有方向,方向:与相同。二.瞬时速度 1.瞬时速度:质点在某一(或某一)速度。瞬时速度可以(“粗略”“精确”)描述运动的快慢。瞬时速度既有大小,又有方向,方向:即为的方向。三.速率和平均速率 1.速率:的大小叫瞬时速率,简称速率,只有大小,没有方向,是量。 2.平均速率:与的比值,不一定等于平均速度的大小。 1.定义:速度的与发生这一变化所用的比值,叫加速度。 2.公式:单位: 3.物理意义:描述速度的物理量。 4.既有大小,又有方向,是量,方向与速度的方向相同。 如有侵权请联系告知删除,感谢你们的配合!

第一章《运动的描述》单元测试题

必修1第一章《运动的描述》单元测试题 一.选择题:(每小题5分,对而不全得3分,共50分) 请将选择题答案填如下列表格内: 1 2 3 4 5 6 7 8 9 10 1 .下列关于质点的说法中,正确的是() A .质点是一个理想化模型,实际上并不存在,所以,引入这个概念没有多大意义。 B. 体积很小、质量很小的物体都可看成质点。 C. 不论物体的质量多大,只要物体的形状和大小对所研究的问题没有影响或影响可 以不略不计,就可以看成质点。 D. 只有低速运动的物体才可看成质点,高速运动的物体不可看作质点。 2 .在下列物体的运动中,可视作质点的物体有() A. 从北京开往广州的一列火车 B.研究转动的汽车轮胎 C.研究绕地球运动时的航天飞机 D.表演精彩芭蕾舞的演员 3 .如图1-1所示,由于风的缘故,河岸上的旗帜在河 面上的两条船上的旗帜分别向右和向左船运动状态是()向右飘,

A ? A 船肯定是向左运动的 B ?A 船肯定是静止的 C ? B 船肯定是向右运动的 D ? B 船可能是静止的 4 .下列关于路程和位移的说法正确的是( ) A .路程是标量,位移是矢量。 B .给定初末位置,路程有无数种可能,位移只有两种可能。 C .若物体作单一方向的直线运动,位移的大小就等于路程。 D .路程是物体运动径迹的长度,位移描述了物体位置移动的方向和距离 5. 如图所示为甲、乙两质点的 v-t 图象。对于甲、乙两质点 的运动,下列说法中正确的是( ) A .质点甲向所选定的正方向运动,质点乙与甲的运动方向 相反 B .质点甲、乙的速度相同 C .在相同的时间内,质点甲、乙的位移相同 D .不管质点甲、乙是否从同一地点开始运动,它们之间的距 离一定越来越大 6. 对于做匀速直线运动的物体,则( ) A. 任意2s 内的位移一定等于1s 内位移的2倍 B. 任意一段时间内的位移大小一定等于它的路程 C. 若两物体的速度相同,贝尼们的速率必然相同,在相同时间内通过的路程相等 D. 若两物体的速率相同,则它们的速度必然相同,在相同时间内的位移相等 7.甲、乙两车沿平直公路通过同样的位移,甲车在前半段位移上以 v 1=40km/h 的速度运动, iWm/s 2 ---------- 甲 1

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