问题
选择题
在“ 验证力的平行四边形定则”实验中,F 1 和F2 表示两个互成角度的力,F表示由平行四边形定则作出的F1和F2的合力,F´表示一个弹簧拉橡皮条时的力,则图中符合实验事实的是( )
答案
答案:A
因为F表示由平行四边形定则作出的F1和F2的合力,则一定在平行四边形的对角线上,F´表示一个弹簧拉橡皮条时的力,则一定与橡皮条的伸长方向在一条直线上,故选A。
在“ 验证力的平行四边形定则”实验中,F 1 和F2 表示两个互成角度的力,F表示由平行四边形定则作出的F1和F2的合力,F´表示一个弹簧拉橡皮条时的力,则图中符合实验事实的是( )
答案:A
因为F表示由平行四边形定则作出的F1和F2的合力,则一定在平行四边形的对角线上,F´表示一个弹簧拉橡皮条时的力,则一定与橡皮条的伸长方向在一条直线上,故选A。
选择和画线部分单词或词语意义相近的选项。 |
1. We eat fast food for lunch at times. |
[ ] |
A. all the time B. sometimes C. some times |
2. What a bright summer morning! |
[ ] |
A. cloudy B. rainy C. sunny |
3. Mike didn't look happy after he saw his grandmother in hospital. |
[ ] |
A. was sad B. was glad C. was sick |
4. At first, I didn't like singing but now I like it very much. |
[ ] |
A. At times B. First C. At the beginning |
5. The old woman felt nervous as she tried to cross the busy road. |
[ ] |
A. worry B. tense C. angry |