问题 选择题

一个圆盘在水平面内匀速转动,盘面上有一个小物体随圆盘一起运动.对小物体进行受力分析,下列说法正确的是(  )

A.只受重力和支持力

B.只受重力、支持力、摩擦力

C.只受重力、支持力、向心力

D.只受重力、支持力、摩擦力、向心力

答案

小木块做匀速圆周运动,合力指向圆心,对木块受力分析,受重力、支持力和静摩擦力,如图

重力和支持力平衡,静摩擦力提供向心力.故B正确,A、C、D错误.

故选B.

改错题

短文改错(共10小题;每小题1分,满分10分)

此题要求改正所给短文中的错误。对标有题号的每一行做出判断:每行只有一个错误,请按下列情况改正:该行多一个词:把多余的词用斜线(\)划掉,在该行右边横线上写出该词,并也用斜线划掉。该行缺一个词:在缺词处加一个漏字符号(),在该行右边横线上写出该加的词。该行错一个词:在错的词下划一横线,在该行右边横线上写出改正后的词。

注意:请在答题卡上作答。

Everyone can do anything for our environment. For me,    76.            

I should tried to save electricity in our daily life. For example, 77.            

if I am the last person leave the classroom in the evening,     78.            

I would always remember to turn off the lights. In order to     79.            

protect our forests, I will use paper wise. I should try  80.            

to use both side of paper whenever it is possible. I will 81.            

ride a bike to school instead of went in a private car,   82.            

because bikes do not pollute the air. I believe that by doing all   83.            

these small things will improve our environment but help  84.            

make our world the much better place to live in.         85.            

76.anything改为:something    77.tried→try。

判断题