5．如图所示，在AB间接入交流电U₁=220V，通过理想变压器和二极管D₁、D₂给阻值R=20Ω的纯电阻负载供电，已知D₁、D₂为相同的理想二极管，正向电阻为0，反向电阻无穷大，变压器原线圈n₁=110匝，副线圈n₂=20匝，Q为副线圈正中央抽头，为保证安全，二极管的反向耐压值至少为U₀，设电阻R上的热功率为P，则有

A．U₀=40V， P=20 W

B．U₀=40V，P=80W

C．U₀=40V， P=80W

D．U₀=40V，P=20 W

4．如图所示，Q是单匝金属线圈，MN是一个螺线管，它的绕线方法没有画出，Q的输出端a、b和MN的输入端c、d之间用导线相连，P是在MN的正下方水平放置的用细导线绕制的软弹簧线圈．若在Q所处的空间加上与环面垂直的变化磁场，发现在t_１至t_２时间段内弹簧线圈处在收缩状态，则所加磁场的磁感应强度的变化情况可能是

D．若有两个这样的飞船在同一轨道上，相隔一段距离一前一后沿同一方向绕行，只

要后一飞船向后喷气加速，则两飞船一定能实现对接

3．2008年9月25日，我国成功发射了“神舟七号”载人飞船，假设飞船绕地球做匀速圆周运动，下列说法中正确的是

A．若知道飞船运动的轨道半径和周期，再利用万有引力常量，就可算出飞船的质量

B．若飞船执行完任务返回地球，在进入大气层之前的过程中，飞船的动能逐渐增大，

引力势能逐渐减小，机械能保持不变

C．若宇航员从船舱中慢慢“走”出并离开飞船，飞船因质量减小，所受万有引力减小，

飞船速率减小

2．如图所示，一根长为l的细绳一端系一小球，另一端悬挂于O点，将小球拉起使细绳与竖直方向成60⁰角，在O点正下方有A、B、C三点，且有．当在A处钉钉子时，小球由静止下摆，被钉子挡住后继续摆动的最大高度为h_A；当在B处钉钉子时，小球由静止下摆，被钉子挡住后继续摆动的最大高度为h_B；当在C处钉子时，小球由静止下摆，被钉子挡住后继续摆动的最大高度h_C，则小球摆动的最大高度h_A、h_B、h_C（与D点的高度差）之间的关系是

A． ==               B． >>

C． >=               D． =>

1．如图所示，小车上有一个定滑轮，跨过定滑轮的绳一端系一重球，另一端系在弹簧秤上，弹簧秤固定在小车上．当小车从静止开始向右做加速度增大的加速运动时，下述说法中正确的是       

A．弹簧秤读数变大，小车对地面压力变大

B．弹簧秤读数变大，小车对地面压力变小

C．弹簧秤读数变大，小车对地面的压力不变

D．弹簧秤读数不变，小车对地面的压力变大

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

书面表达（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.

短文改错     56. and改为but  57. woman改为women   58. called前加have