如图，建筑工人用恒力F推运料车在水平地面上匀速前进，F与水平方_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题选择题

如图，建筑工人用恒力F推运料车在水平地面上匀速前进，F与水平方向成30°角，运料车和材料的总重为G，下列说法正确的是（　　）

A．建筑工人受摩擦力方向水平向左

B．建筑工人受摩擦力大小为

3

2

G

C．运料车受到地面的摩擦力水平向右

D．运料车对地面压力为

F

2+G

答案

以人为研究对象，分析人的受力情况，如图1，由平衡条件得：人受到的摩擦力方向水平向右，大小为f_人=Fcos30°=

3

2

F．

分析运料车和材料的受力情况，作出受力图，如图2，由平衡条件得：运料车受到地面的摩擦力水平向左，地面对运料车的支持力大小为N_车=G+Fsin30°=

F

2

+G，则运料车对地面压力为

F

2

+G．故D正确，ABC均错误．

故选D

阅读理解

阅读下列短文，根据其内容完成后面各项任务。

These days, more and more young people wish to be more beautiful, so they turn to plastic surgery(整形手术)for help. They spend thousands of yuan ① these painful surgeries to fix their nose, to change their eyelids(眼皮) or to take off weight from their stomachs.

②In fact most people are not pleased with the way they look. Even ③最美丽actresses often wish they could change something about their looks. Should we live our whole lives believing we are ugly? Why can’t we raise our head high and believe that we are as beautiful as others? A smile is beautiful on my face, whether fat, oily or hairy. And a kind heart is much more beautiful than a pretty look. So, let’s feel grateful that we all have beautiful and healthy bodies that do not need surgeries! Today, I call on you to make an easy change: hold your head high, smile and be kind to others. If you do these, you will ④be full of confidence, beauty, and warmth everywhere you go.

小题1:请在①处填上一个正确的介词。

小题2:请将②处句子译为汉语。

小题3:请将③处短语译为英语。

小题4:写出④处的同义词语

小题5:判断正（T）误(F).

（）The writer thinks a pretty look is much more beautiful than a kind heart.

判断题

三氟化硼是属于路易斯酸。