8．如图4所示，两木块A、B用轻质弹簧连在一起，置于光滑的水平面上．一颗子弹水平射入木块A，并留在其中．在子弹打中木块A及弹簧被压缩的整个过程中，对子弹、两木块和弹簧组成的系统，下列说法中正确的是

A．动量守恒、机械能守恒　　　 B．动量守恒、机械能不守恒

C．动量不守恒、机械能守恒　 　D．动量、机械能都不守恒

7. 如图所示为交变电流随时间而变化的图象，其中电流的正值是正弦曲线的正半周，最大值为2A；电流的负值大小为2A，则该交变电流的有效值为

A． A　　　　　　　　　　　　　　　 B．2A

C． A　　　　　　　　　　　　　　 D．2A

6.如图所示,大量氢原子处于能级n=4的激发态,当它们向较低能级跃迁时,对于多种可能的跃迁,下面说法中正确的是

A.从n=4能级跃迁到n=2能级放出的光子的频率等于从n=2能级跃迁到n=1能级放出的光子的频率

B.最多只能放出3种不同频率的光子

C.从n=4能级跃迁到n=1能级放出的光子频率最高

D.从n=4能级跃迁到n=1能级放出的光子波长最长

5．质量分别为2m和m的A、B两个质点，初速度相同，均为v₁.若他们分别受到相同的冲量I作用后，A的速度为v₂，B的动量为p.已知A、B都做直线运动，则动量p可以表示为

A．m(v₂－v₁)　　B．2m(2v₂－v₁)　　　 C．4m(v₂－v₁)　 　　 　D．m(2v₂－v₁)

4.远距离输电时，在输送的电功率和输电线电阻一定的条件下，输电线上损失的电功率

A．与输电电压的平方成正比　　　　　　　　　 　B．与输电电压的平方成反比

C．与输电电压成正比　　　　　 　　　　　　 D．与输电电压成反比　　　

3. 如图为一理想变压器, 其原副线圈匝数比n₁∶n₂＝1∶10, 副线圈与阻值R＝20 Ω的电阻相连。原线圈两端所加的电压u＝20 sin100πt(V), 则

A. 交流电压表的示数为20 V

B. 副线圈输出交流电的频率为100 Hz

C. 电阻R上消耗的电功率为2 kW

D. 原线圈中电流的最大值为100 A

一、单选题

1. 下列说法中正确的是

A．爱因斯坦提出了能量量子化理论

B．光在传播过程中能量是连续的

C．光电效应和康普顿效应均揭示了光具有粒子性

D．升高或者降低放射性物质的温度均可改变其半衰期

2. 如图所示，一木块放在光滑水平面上，一子弹水平射入木块中，射入深度为d，

平均阻力为f.设木块离原点s远时开始匀速前进，下列判断正确的是

A．fs量度子弹损失的动能

B．fd量度子弹损失的动能

C．f（s＋d）量度木块获得的动能

D．fd量度子弹、木块系统总机械能的损失

D

65. Why is June 6, 1990 a special day for Mommy?

A. Her dream of being a mother came true.

B. She found her origin from her Chinese mother.

C. She wrote the letter to her daughter.

D. Her female line was well linked.

66. How does Mommy feel about her being given away?

A. It is bitter and disappointing.

B. It is painful but understandable.

C. She feels sorry but sympathetic.

D. She feels hurt and angry.

67. What does “I stood out like a sore thumb” in Paragraph 5 mean?

A. I walked clumsily out of pains.

B. I was not easy to love due to jealousy.

C. I was impatient out of fear.

D. I looked different from others.

68. What can be inferred from Mommy’s Anglo family life?

A. She used to experience an identity crisis.

B. She fought against her American identity.

C. She forgot the pains of her early years.

D. She kept her love for Asia from childhood.

69. Why did Mommy name her daughter “Shao-ming?”

A. To match her own birth-name.

B. To brighten the lives of the family.

C. To identify her with Chinese origin.

D. To justify her pride in Chinese culture.

70. By “Your past is more complete than mine,” Mommy means ________.

A. her past was completed earlier than Shao-ming’s

B. Shao-ming has got motherly care and a sense of roots

C. her mother didn’t comfort her the way she did Shao-ming

D. her past was spent brokenly, first in Asia, then in the US