问题 选择题

如图所示,红蜡块可以在竖直玻璃管内的水中匀速上升,若在红蜡块从A点开始匀速上升的同时,玻璃管水平向右做匀速直线运动,则红蜡块的实际运动轨迹可能是图中的(  )

A.直线P

B.曲线Q

C.曲线R

D.三条轨迹都有可能

答案

当合速度的方向与合力(合加速度)的方向不在同一条直线上,物体将做曲线运动,且轨迹夹在速度与合力方向之间,轨迹的凹向大致指向合力的方向.

而本题两个方向均做匀速直线运动,因此蜡块将沿着合速度的方向做匀速直线运动,知A正确,B、C、D错误.

故选A.

阅读理解

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余项。

What is your favorite color? Do you like yellow, orange, and red?  71  Do you prefer grays and blues? Then you are probably quiet, shy, and you would rather follow than lead. You tend to be a pessimist(悲观者). At least, this is what psychologists(心理专家) tell us, and they should know, because they have been seriously studying the meaning of colors preference, as well as the effect that colors have on human beings.   72 If you happen to love brown, you did so, as soon as you opened your eyes, or at least as soon as you could see clearly.

 73  A yellow room makes most people feel more cheerful and more relaxed than a dark green one; and a red dress brings warmth and cheer to the saddest winter day.  74  A black bridge over the Thames River, near London, used to be the scene of more suicides than any other bridge in the area ---until it was repainted green. The number of suicide attempts immediately fell sharply; perhaps it would have fallen even more if the bridge had been done in pink or baby blue.

  75 It is an established fact that factory workers work better, harder, and have fewer accidents when their machines are painted orange rather than black or grey.

A.On the other hand, black is depressing.

B.They tells us that we do not choose our favorite color as we grow up——we are born

with our preference.

C.The rooms are painted in different colors as you like.

D.If you do, you must be an optimist(乐观者), a leader, an active person who enjoys life, people and excitement.

E. Light and bright colors make people not only happier but more active.

F. Life is like a picture or a poem, full of different colors.

G. Colors do influence our moods——there is no doubt about it .

判断题