问题
选择题
质量60kg的人通过光滑的定滑轮拉动质量20kg的物体，如图所示，当物体以5m/s２的加速度加速上升时，人对地面的压力等于（g=10m/s2）
A．300N
B．800N
C．600N
D．400 N
答案
答案：A
对物体受力分析有：
，
，对人受力分析有：
，N=300N，A正确。
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质量60kg的人通过光滑的定滑轮拉动质量20kg的物体，如图所示，当物体以5m/s２的加速度加速上升时，人对地面的压力等于（g=10m/s2）
A．300N
B．800N
C．600N
D．400 N
答案：A
对物体受力分析有：，，对人受力分析有：，N=300N，A正确。
| 完形填空。 | |||
| Anyone may 1 a bad day. Two young thieves were walking in the street 2 a cold, dark winter evening together. They tried their best 3 a chance to steal something from the rich house. By the time the clock struck twelve, most of the people 4 to bed. After a short time, they came to a very beautiful and quiet house whose owner must have a lot of money. And it seemed that everyone in the house had fallen 5 . When they stood at the front gate, one thief said in English to 6 in a low voice, "You wait here. I'll go around to the back door and then get into the house. " Suddenly out the house ran a dog 7 was barking at them loudly. The two men were so 8 of dogs that they ran away as fast as they could. Twenty minutes later, they were too exhausted to run any further. 9 they stopped to have a rest at a dark corner. One man said breathlessly, "It's too bad. I hadn't expected that the dog could understand English so well." The other said, How 10 you are You shouldn't speak English to me. You should have used body language(身势语). " | |||
| ( )1. A. have ( )2. A. in ( )3. A. finding ( )4. A. went ( )5. A. slept ( )6. A. another ( )7. A. what ( )8. A. terrified ( )9. A. But ( )10. A. foolish | B. has B. at B. to find B. was going B. asleep B. other B. where B. terrifying B. And B. fool | C. had C. from C. find C. goes C. sleepy C,. the others C. that C. terrible C. Because C. foolishly | D. having D. on D. found D. had gone D. sleep D. the other D. why D. worried D. So D. clever |