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问题 计算题

如图所示，底座A上装有长0.5m的直立杆，总质量为0.2kg，杆上套有质量为0.05kg的小环B，它与杆有摩擦，当环从底端以4m/s的速度升起时刚好能到达顶端。求：（g = 10m／s2）

（1）在环升起过程中，底座对水平面的压力为多大？

（2）小环从杆顶落回底座需多少时间？

答案

解：（1）

联立以上三式解得FN= 1.7N

由作用力和反作用力关系，底座对水平面的压力FN′=FN = 1.7N

（2）

联立以上二式解得下落时间t = 0.5s

单项选择题

将一定质量的气体的（）、温度联系起来的方程式叫气体状态方程式.

A.压力、密度

B.压力、体积

C.压力、重量

D.体积、密度
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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.

12（）

A.connection

B.reach

C.association

D.touch
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