题目

如图所示，A、B两个物块叠放在光滑水平地面上，质量分别是2kg和4kg，它们之间的动摩擦因数为0.2，设最大静摩擦力等于滑动摩擦力，取g=10m/s2 ． 现对A施加水平拉力F，要保持A、B相对静止，F不能超过（） A . 2N B . 4N C . 6N D . 8N 答案：C Welcome to Made-in-China website! Tea pot Color: White Price: ¥ 120 Delivery (递送）time: 10 work days after received 30% payment. Tea pots with good quality. And the best gift for your friends or your family. Handbag Color: Black-and white Price: ¥ 280 (¥ 520 for two on Women’s Day) Delivery time: 7 days after confirmation (认证） We have our own designers. Our new styles may give you a new surprise. 2013 Newly Children Bicycle Color Blue Price: ¥ 240 (20% off on Children’s Day) Delivery time: 5 days after confirmation With a basket for children aged from 3-7 New Design Fashion Button Color: All kinds of colors Price: Y 1.00 (¥9 for ten) Delivery time: 3 days after confirmation New and popular designs, you can dye them into different colors if you like. 1 Where can you buy these things according to the ad? A. In a shop.        B. In a mall.           C. On the Internet.   D. In a supermarket. 2 From the ad, you can buy the children bicycle for a child of __________. A. 2               B. 5                     C.8               D. 10 3 The best birthday gift for your grandpa is __________. A. some buttons      B. a handbag      C. a tea pot           D. a children bicycle 4 My mother ordered some fashion buttons, and she can get them __________ days later. A. three                  B. five             C. seven                 D. ten 5 If you have Y 400, you can buy __________. A. two handbags                         B. 500 buttons C. a handbag and a bicycle                 D. a tea pot and a handbag