【单选题】
一物块重P，放在粗糙的水平面上，其摩擦角max=20°，若力F作用于摩擦角之外，且已知力F=P，F与水平面的夹角为q=30°，则物体()。(注：物块不会翻倒)
①
能保持静
②
不能保持静止
③
处于临界状态
④
P与F的值较小时能保持静止，否则不能
【单选题】
直线AB的正面投影与OX轴倾斜，水平投影与OX轴平行，则直线AB是( )
①
Normal
0
7.8 磅
0
2
false
false
false
EN-US
ZH-CN
X-NONE
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水平线
②
Normal
0
7.8 磅
0
2
false
false
false
EN-US
ZH-CN
X-NONE
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正平线
③
Normal
0
7.8 磅
0
2
false
false
false
EN-US
ZH-CN
X-NONE
侧垂线
④
Normal
0
7.8 磅
0
2
false
false
false
EN-US
ZH-CN
X-NONE
/* Style Definitions */
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一般位置线
【单选题】
平面P在（ ）面上的投影反映实形，因此称之为水平面。<img src=https://huaweicloudobs.ahjxjy.cn/F2AABBA0431B209EC3B47E0938D54BEA.png title=图片1.png alt=图片1.png style=width: 349px; height: 198px; width=349 height=198/>
①
正投影
②
水平投影
③
侧投影
④
一般位置