问题 单项选择题

用绳系一个小球,使它在光滑水平桌面上绕O点做匀速圆周运动.小球运动到A点时绳突然断裂,则此后小球将()

A.沿轨迹1运动

B.沿轨迹2运动

C.沿轨迹3运动

D.沿轨迹4运动

答案

参考答案:A

解析:根据牛顿第一定律可知:当物体不受力时,将保持匀速直线运动状态或静止状态;光滑的水平面没有摩擦,当绳子突然断裂,在水平方向上,不受拉力和摩擦力;在竖直方向上,受到的重力和支持力是一对平衡力,大小相互抵消;故小球相当于不受力,将保持绳子断裂时的速度做匀速直线运动.当绳子突然断裂,在水平方向上,不受拉力和摩擦力;在竖直方向上,受到的重力和支持力是一对平衡力,大小相互抵消;故小球相当于不受力,将保持绳子断裂时的速度做匀速直线运动.故A正确.故选A.

阅读理解

Great leaders are almost always great simplifiers, who cut through argument, debate and doubt to offer a solution everybody can understand and remember.Churchill warned the British to expect “blood, toil, tears and sweat”; Roosevelt told the Americans that “the only thing we have to fear is fear itself”; Lenin promised the war-weary Russians peace, land and bread.Straightforward but effective messages.

We have an image of what a leader ought to be.We even recognize the physical signs; leaders may not necessarily be tall, but they must have bigger-than-life, commanding features -- Lyndon Baines Johnson’s nose and ear lobes, Ike’s broad grin.A trade-mark also comes in handy; Lincoln’s stovepipe hat, Kennedy’s rocking chair.We expect our leaders to stand out a little, not to be like an ordinary man.Half of President Ford’s trouble lay on the fact that, if you closed your eyes for a moment, you couldn’t remember his face, figure of clothes.A leader should have an unforgettable identity, instantly and permanently fixed in people’s minds.

It also helps for a leader to be able to do something most of us can’t: FDR overcame polio; Mao swam the Yangtze River at the age of 72. We don’t want our leaders to be "just like us." We want them to be like us but better, special more so. Yet if they are too different, we reject them.

A Chinese philosopher once remarked that a leader must have the grace of a good dancer, and there is a great deal of wisdom to this. A leader should know how to appear relaxed and confident. His walks should be firm and purposeful. He should be able, like Lincoln, Roosevelt, Truman, Lke and JFK, to give a good, hearty, belly laugh, instead of the sickly grin that passes for good humor in Nixon or Carter. Ronald Reagan’s training as an actor showed to good effect in the debate with Carter, when by his easy manner and apparent affability, he managed to convey the impression that in fact he was the president and Carter the challenger.

The every simple truth about leadership is that people can only be led where they want to go. The leader follows, though a step ahead. Americans wanted to climb out of the Depression and needed someone to tell them they could do it, and Roosevelt did. The British believed that they could still win the war after the defeats of 1940, and Churchill told them they were right.

A leader rides the waves, moves with the tides, understands the deepest yearning of his people. He cannot make a nation that wants peace at any price go to war, or stop a nation determined to fight from doing so. His purpose must match the national mood.

1.The underlined word “yearning” in the last paragraph probably means_________.

A.love  B.trouble     C.desire       D.feeling

2.From the fourth paragraph we can learn that_________.

A.leaders usually look special or different

B.leaders don’t have to be tall

C.most leaders look ordinary

D.leaders should always have trademarks

3.According to the article, a leader_________.

A.usually tries to simplify our messages

B.tell us what we want to hear

C.encourages us to think about things in a new way

D.is usually confident and handsome

4.From the passage we can infer that          .

A.it helps for a leader to be able to dance or act well

B.great leaders are usually totally different from us

C.Carter was humorous and made good speeches

D.it is the people rather than the president that makes what a nation is

5.Which of the following can be the best title for the passage?

A.Want to be a leader?

B.What makes a leader?

C.What does a leader look like?

D.What must a leader do?

单项选择题 A1/A2型题