5．如圖所示，在AB間接入交流電U₁=220V，通過理想變壓器和二極管D₁、D₂給阻值R=20Ω的純電阻負載供電，已知D₁、D₂為相同的理想二極管，正向電阻為0，反向電阻無窮大，變壓器原線圈n₁=110匝，副線圈n₂=20匝，Q為副線圈正中央抽頭，為保證安全，二極管的反向耐壓值至少為U₀，設電阻R上的熱功率為P，則有

A．U₀=40V， P=20 W

B．U₀=40V，P=80W

C．U₀=40V， P=80W

D．U₀=40V，P=20 W

4．如圖所示，Q是單匝金屬線圈，MN是一個螺線管，它的繞線方法沒有畫出，Q的輸出端a、b和MN的輸入端c、d之間用導線相連，P是在MN的正下方水平放置的用細導線繞制的軟彈簧線圈．若在Q所處的空間加上與環(huán)面垂直的變化磁場，發(fā)現(xiàn)在t_１至t_２時間段內(nèi)彈簧線圈處在收縮狀態(tài)，則所加磁場的磁感應強度的變化情況可能是

D．若有兩個這樣的飛船在同一軌道上，相隔一段距離一前一后沿同一方向繞行，只

要后一飛船向后噴氣加速，則兩飛船一定能實現(xiàn)對接

3．2008年9月25日，我國成功發(fā)射了“神舟七號”載人飛船，假設飛船繞地球做勻速圓周運動，下列說法中正確的是

A．若知道飛船運動的軌道半徑和周期，再利用萬有引力常量，就可算出飛船的質(zhì)量

B．若飛船執(zhí)行完任務返回地球，在進入大氣層之前的過程中，飛船的動能逐漸增大，

引力勢能逐漸減小，機械能保持不變

C．若宇航員從船艙中慢慢“走”出并離開飛船，飛船因質(zhì)量減小，所受萬有引力減小，

飛船速率減小

2．如圖所示，一根長為l的細繩一端系一小球，另一端懸掛于O點，將小球拉起使細繩與豎直方向成60⁰角，在O點正下方有A、B、C三點，且有．當在A處釘釘子時，小球由靜止下擺，被釘子擋住后繼續(xù)擺動的最大高度為h_A；當在B處釘釘子時，小球由靜止下擺，被釘子擋住后繼續(xù)擺動的最大高度為h_B；當在C處釘子時，小球由靜止下擺，被釘子擋住后繼續(xù)擺動的最大高度h_C，則小球擺動的最大高度h_A、h_B、h_C（與D點的高度差）之間的關系是

A． ==               B． >>

C． >=               D． =>

1．如圖所示，小車上有一個定滑輪，跨過定滑輪的繩一端系一重球，另一端系在彈簧秤上，彈簧秤固定在小車上．當小車從靜止開始向右做加速度增大的加速運動時，下述說法中正確的是       

A．彈簧秤讀數(shù)變大，小車對地面壓力變大

B．彈簧秤讀數(shù)變大，小車對地面壓力變小

C．彈簧秤讀數(shù)變大，小車對地面的壓力不變

D．彈簧秤讀數(shù)不變，小車對地面的壓力變大

59. play改為playing      60. 正確        61. feel改為feeling      62. how改為why     63. make改為makes     64. 去掉the     65. sell改為buy

書面表達（范文）：

We often give money to the people in poor or disaster-stricken areas. Some students don’t think it a good way to help people there. However, some prefer helping the unfortunate with money.

In their opinion, money can be used to buy daily necessities and can help people rebuild their hometowns, while sometimes the things people there receive are not what they need actually. But some other students think that giving used clothing to the people in those areas is better. Many people, especially in rich areas and in cities, have much clothing they no longer like or need. By giving it away to the needy people we can make the best use of it. Besides, we are just students, and we have no incomes of our own.

Anyhow, no matter which way is considered better, we should try our best to help those who need help.

短文改錯     56. and改為but  57. woman改為women   58. called前加have