问题
选择题
| 如图所示，AB是一质量为m的均匀细直杆，A端靠在光滑的竖直墙壁上，B端置于水平地面上，杆身与竖直方向夹角为θ，杆与地面的摩擦系数为μ，保持平衡，则此时杆与地面的摩擦力为（ ） A． B． C． D．μmg  |
mgtgθ
mgsinθ
答案
答案：A
搜题请搜索小程序“爱下问搜题”
| 如图所示，AB是一质量为m的均匀细直杆，A端靠在光滑的竖直墙壁上，B端置于水平地面上，杆身与竖直方向夹角为θ，杆与地面的摩擦系数为μ，保持平衡，则此时杆与地面的摩擦力为（ ） A． B． C． D．μmg |
答案：A
| 完形填空。 | |||
| I and five other travelers spent one week in Tunisia, in March, 1998. Our group was 1 in experiencing the history and sunbathing. At first we made a reservation (预订) for a 2 to Luxor, Egypt, for the autumn of 1997. The trip was cancelled (取消) by the travel agency, 3 a terrorist attack (袭击), which took place in Luxor, 4 we needed to change our plans. We wanted sun, ancient 5 and all for less than $500 a week. We did not have a lot of 6 , and so we decided to travel to Tunisia. As it turned out (证明), that was not at all a bad decision. When we left for Tunisia we did not have any "deep" 7 of the country, its history or its culture, but once we got there we 8 it very interesting. We saw ruins (废墟) from the Roman Empire, the ruined towns of Dougga, Thuburbo Majus, Carthage and Sbeitla. With a little time and some patience, these places 9 a lot to see. 10 of all, most of the places allow visitors to walk around the ruins. So if you are really interested in the history of the Roman Empire, Tunisia is the place to go. | |||
| ( )1. A. interested ( )2. A. trouble ( )3. A. for example ( )4. A. though ( )5. A. buildings ( )6. A. dreams ( )7. A. root ( )8. A. lit ( )9. A. offer ( )10. A. Good | B. worried B. journey B. in general B. but B. games B. choices B. step B. put B. form B. Best | C. excited C. mistake C. because of C. or C. marks C. noises C. understanding C. got C. lend C. Better | D. bored D. friend D. for instance D. so D. poems D. tasks D. wave D. found D. invent D. Well |