问题 填空题

在“研究共点力的合成”的实验中,需要将橡皮条的一端固定在水平木板上,另一端系上两根细绳,细绳的另一端都有绳套.实验中需用两个弹簧测力计分别勾住绳套,并互成角度地拉橡皮条,使橡皮条的另一端拉到某一确定的O点.某同学认为在此过程中必须注意以下几项,其中正确的是 (  )(填入相应的字母)

A.两根细绳必须等长

B.同一实验过程中,O点位置允许变动

C.实验中,弹簧秤必须与木板平行,读数时视线要正对弹簧秤刻度线

D.实验中,把橡皮条另一端拉到O点时,两弹簧秤之间的夹角应取90°,以便于算出合力大小

答案

A、细线的作用是能显示出力的方向,所以不必须等长.故A错误.

     B、本实验研究合力与分力的关系,合力与分力是等效的,同一次实验过程中,O点位置不能变动,以保证橡皮筯伸长的长度相同,效果相同.故B错误.

     C、本实验是通过在白纸上作力的图示来验证平行四边定则,为了减小实验误差,弹簧秤、细绳、橡皮条都应与木板平行,否则,作出的是拉力在纸面上的分力,误差较大.读数时视线必须与刻度尺垂直,防止视觉误差.故C正确.

     D、只要橡皮筋的另一端两次都接到O点,达到效果相同,拉力方向没有限制,两弹簧秤之间的夹角不需要取90°,故D错误.

故选C

完形填空

Happiness is for everyone. You don’t need to care about the       . Though they have beautiful houses with large gardens and swimming pools, they may often feel       .

In fact,      is always around you if you put your heart into it. When you are in         at school, your teachers will help you; when you do something wrong, people        you feel unhappy; when you        in something, your friends will say congratulations to you. All these are your happiness. If you notice a bit of them, you can see       happiness is always around you.

Happiness is not the same as money. It is a feeling of your heart.      you are poor, you can also say you are very happy. Money is not       . You have something else that money can’t buy. When you meet with difficulties, you can loudly say you are very happy because you have more chances to challenge       . So you can not always say you are poor and you have bad luck. If you take every chance you get, you can be a happy and lucky person.

小题1:

A.poor

B.old

C.rich

D.young小题2:

A.alone

B.happy

C.sad

D.lonely小题3:

A.sadness

B.happiness

C.loneliness

D.unhappiness小题4:

A.trouble

B.difficult

C.happy

D.sad小题5:

A.beside

B.around

C.besides

D.by小题6:

A.fail

B.get

C.make

D.succeed小题7:

A.that

B.which

C.what

D.why小题8:

A.But

B.However

C.Although

D.And小题9:

A.anything

B.everything

C.something

D.nothing小题10:

A.yourself

B.you

C.myself

D.me

多项选择题