题型：问答题 A、B两物体在光滑水平地面上沿一直线相向而行，A质量为5kg，速度大小为10m/s，B质量为2kg，速度大小为5m/s，它们的总动量大小为__________________kgm/s：两者碰撞后，A沿原方向运动，速度大小为4m/s，则B的速度大小为__________________m/s。 查看答案
题型：问答题 完型填空. When you are in England, you must be careful in the streets because traffic drives on the left. __1__ you cross a street, you must look to the right first and then left. If the traffic lights are __2__, the traffic must stop. Then the people on the foot can cross the road __3__.If the traffic lights are green, the traffic can go on, people on foot __4__cross.In the morning and in the evening, when people go to or from work, the streets are very __5__.Traffice is most dangerous then. When you go by bus in England, you have to be carefully, too. Always remember that traffic moves on the __6__. So you must be careful. Have a look first, __7__ you will go the wrong __8__. In many English cities, there are big buses __9__ floors. You can sit on the __10__ floor. From there you can see the city very well. It's very interesting.( )1. A. Before( )2. A. black( )3. A. care( )4. A. can ( )5. A. busy( )6. A. left( )7. A. because( )8. A. street( )9. A. in( )10. A. firstB. AfterB. redB. carefulB. couldB. bigB. rightB. orB. parkB. orB. secondC. BetweenC. g reenC. carefullyC. must notC. safeC. frontC. so thanC. roadC. withC. thirdD. Unit l D. yellow D. more carefulD. have to D. wide D. back D. either D. way D. on D. fourth 查看答案