问题 问答题

学习了物体动能概念后,有同学猜测物体动能与其质量、速度有关,于是做了钢球从斜面滚下推动木块的对比验证实验,其中有下列操作,试回答这些操作目的.

①钢球从不同高度滚下,目的是为了______,从而探究物体动能与______的关系.

②换用同体积的铝球代替钢球从同一高度滚下,目的是______,从而探究物体动能与______的关系.

答案

①钢球从不同高度滚下,到达水平面获得的初速度不同,这样控制质量相同,改变钢球的速度大小,所以目的是为了改变钢球的初始速度,从而探究物体动能与速度的关系.

②铝球和钢球从同一高度滚下,到达水平面获得的初速度相同,球的质量不同,目的是使球具有相同的初始速度,从而探究物体动能与质量的关系.

故答案为:①改变钢球的初始速度,速度.②使球具有相同的初始速度;质量.

单项选择题

A recent poll indicated that half the teenagers in the United States believe that communication between them and their parents is (1) and further that one of the prime causes of this gap is (2) listening behavior. As a(an) (3) in point, one parent believed that her daughter had a severe (4) problem. She was so (5) that she took her to an audiologist to have her ear tested. The audiologist carefully tested both ears and reported back to the parent:"There’s nothing wrong with her hearing. She’s just (6) you out. "

A leading cause of the (7) divorce rate (more than half of all marriages end in divorce) is the failure of husbands and wives to (8) effectively. They don’t listen to each other. Neither person (9) to the actual message sent by the other.

In (10) fashion, political scientists report that a growing number of people believe that their elected and (11) officials are out of (12) with the constituents they are supposedly (13) Why Because they don’t believe that they listen to them. In fact, it seems that sometimes our politicians don’t even listen to themselves. The following is a true story: At a national (14) conference held in Albuquerque some years ago, then Senator Joseph Montoya was (15) a copy of a press release by a press aide shortly before he got up before the audience to (16) a speech. When he rose to speak, (17) the horror of the press aide and the (18) of his audience, Montoya began reading the press release, not his speech. He began, "For immediate release. Senator Joseph M. Montoya, Democrat of New Mexico, last night told the National... " Montoya read the entire six page release, (19) with the statement that he "was repeatedly (20) by applause.

11()

A.nominated

B.selected

C.appointed

D.supported

多项选择题