题干

弹簧振子在做简谐振动的过程中,振子通过平衡位置时 (       )

A:速度值最大

B:回复力的值最大

C:加速度值最大

D:位移最大

上一题 下一题 0.0难度 选择题 更新时间:2017-07-05 12:44:20

答案(点此获取答案解析)

A

同类题4

阅读下文,完成下面小题。

天空的道路

傅菲

    ①到瓢里山,已是傍晚,雪花铺在草坪上,一片银白。瓢里山,一个漂浮在水上的名字,一座誉为候鸟天堂的内湖小岛,它就像悬挂在都阳湖白沙洲上的一个巨大鸟巢。岛上没有酒店,向导把我送到他的一个叫鲅鱼的朋友家夜宿。

    ②我是个热爱城市生活的人,尤其我居住的小城,信江穿城而过,山冈成蕤,但我还是像患了周期性躁郁症一样,不去乡间走走,很容易暴躁。——我不知道城市生活缺少了什么,或者说,心灵的内环境需要一种什么东西来填充。今年二月,我正处于这种焦灼的状态,一场意外的雪,给了我去鄱阳日湖的理由——去看一场湖光雪景,群鸟歌舞。

    ③被范仲淹誉为“小南海”的瓢里山,屋舍稀落,掩映在“白”树从中。树是槐树和香樟,高大、浓密,从视野里喷涌而出,像披戴雪花编织的帽子,远远望去,仿佛是一片在银色湖面上游弋的船帆。白鹭、天鹅、鹳、鹤,不时惊起,俯冲低空,与灰茫茫的天空、白皑皑的草地融为一体。皱鱼的房子是用鸫卵石砌的,房顶用密密匝匝的芦节盖实,屋后的小院通往一片开阔的鱼塘。鲅鱼对我的意外造访,很是兴奋,说:“僻壤之地,喝点酒驱驱寒吧。”鲅鱼的房子不大,有四个房间。我们喝酒的厅堂摆了三只塑料桶,和一辆破旧的自行车,壁上悬着一个马灯和一个可以戴在头上的矿灯。塑料桶里分别放着田螺、泥鳅和小鱼。鲅鱼说,这些是给客人吃的。西房是卧室,有一个书橱,满满地排列着有关鸟类的书,还有一个药橱,放着药瓶和纱布。

    ④鲅鱼四十五六岁,戴一副黑边眼镜,土墩一样厚实,皮肤黝黑,手指短而粗,他一边喝酒一边说起他自己的事。他原来在城里的一个文化单位上班,经常陪一些摄影家到瓢里山采风。有一年冬天,他听说一个年轻人为了抓那些猎鸟的人,在草地上守候了三夜,在抓人时被盗贼用猎枪打死,身上布满密密麻麻的硝孔。之后,鲅鱼选择了这里,在年轻人当年蒙难的地方,盖了这片陋舍,辞了职,离了家,与鸟为邻,与湖为伴。湖边的夜晚,犹如糨糊,浓稠,黏湿。呼啦啦的风扑打着门窗,窗外银白蒙蒙那是寂静和落寞的颜色。东边的房子里传来嘎嘎嘎的鸟叫声,鲅鱼说,那是鹳饿了。鲅鱼提着鱼桶,往东房走去。我也跟着去。东房铺了一张床,床上有四只鸟,鸟的身上穿着旧衣服缝制的小袄,样子有点滑稽。鲅鱼说,这几只鸟都是受过伤的,怕冷。他又说:“不同的乌叫声不同,体形和颜色也不同。天鹅形状似鹅,呃呃呃地叫,像歌女练声,体形较大,全身白色,上嘴分黄色和黑色两部分,脚和尾都短,脚黑色,有蹼。白鹭羽腿很长,啊响啊,叫声里透露出一种孤独。鹳嘴长而直,羽毛灰色或白色或黑色。鹤头小颈长,叫声尖细,嗨嗨嗨,羽毛灰色或白色。”

    ⑤这四只鸟,像失散离家的孩子,一看见鲅鱼,就像见了双亲,格外亲热一一伸长脖子,张开细长的嘴,一阵欢叫。我辨得出,这是三只鹳和一只白鹤,它们就是鲅鱼的“客人”吧。鲅鱼把小鱼一条条地送到“客人”的嘴里,脸上游弋着捉摸不定的微笑。他一边喂食一边抚摸这些“客人”的脖颈。鲅鱼说,这四只鸟已经养了一个多月,伤口愈合了,但体质还没恢复,等过了雪季,阳春通暖,它们就可以回归自然,回到它们的另一个故乡。他的声调是散淡的,夹裹着幸福的忧伤。

    ⑥这个夜晚注定是漫长的——不是因为雪夜的惆怅和荒野的孤寂。我甚至想象不出,候鸟迁徙到西太平洋的时候,他是怎样生活的。他会不会一边割草养鱼,一边默念着时光,等待候鸟的来临?瓢里山的等待一年比一年荒老,这样的荒老是一种坚韧,也是一种信仰。我反复咀嚼鲅鱼说的一件事:2000年冬,鲅鱼救护了一只丹顶鹤,养了两个多月,日夜看护,到迁徙时放飞了,第二年十月,这只丹顶鹤平早地来了,整天在院子里夫来走去,鲅鱼一看到它,紧紧地把它抱在怀里。以后每年,它都在鲅鱼家度过一个肥美的冬季。去年,丹顶鹤再也没来,鲅鱼失魂落魄,还为此喝闷酒,醉过不止一回。

    ⑦第二天早晨,太阳彤红地升起,浑圆、壮阂,映衬着无边的雪光,乌群遮蔽了天空,郄阳湖的涛声远远传来,依然令人惊骇。乌声此起彼伏,像音乐的海洋。我想起泰戈尔老人的话:上岸之前,我们是陌生人;来到你的岸上,我是你的宾客;离开你的岸,我们是朋友。

    ⑧那一只只鸟,就像一团团白色的火焰,在燃烧。天空布满了鸟的道路,大地上也一样。(有删改)

同类题5

阅读下列短文,从每小题所给的A、B、C、D四个选项中选出一个最佳选项。

Going Green

    Green is no longer just a color. It is a new way of thinking about the world and a way of living your life. It's catching on all over the world. More and more people decide to “go green” because they know that we only have one planet to live on. We won't be able to live on it much longer if we keep wasting energy, and destroying(破坏) our home with air, land, and water pollution.

    “Green Living” means:

    Understanding that your choices affect(影响) not just you, but everybody everywhere.

    Understanding that your choices affect not just today, but the future.

    Understanding that when we talk about “saving the planet” or “saving the environment,” we are actually talking about saving ourselves!

    You may be thinking: “Hey, I'm just one person, on a planet with billions. I can't really make a difference.” Well, have you ever seen a group of people do “the wave(波浪)”? It always starts off with one or two people, jumping up and down like crazy. Soon thousands of people are joining in. “Going green” is just like that. It starts with small, simple actions. It can soon build into a wave that will change the whole planet and lead us all to healthier, happier lives.

    Many students have already shared with us their efforts to help the environment:

    Gabrielle, 12, writes, “I have helped my community plant a garden and I ride my bike or skateboard to school.”

    Kaitlyn, 10, says, “Lots of paper towels are thrown away, so I use a reusable cloth towel to dry my hands instead.”

    “I always recycle(重复利用)” says Natalie, 13. “You can call me a recycler! I always look at the bottom of things. I want to see whether they have the little sign that tells you it can be recycled. So I almost recycle everything!”

    Now it's your turn to think about how you can “go green”. Make important choices and take actions to improve the environment right around you and the health of the whole world.