题目

小华同学用100N的水平推力，推放在水平地面上重500N的物体，使其作匀速直线运动．若该物体在10s内移动5m，则在此过程中它的速度为      m／s，小华做功的功率是       W．  答案：0.5   50解析:用100N的水平推力，推放在水平地面上重500N的物体，使其作匀速直线运动．若该物体在10s内移动5m，则在此过程中它的速度为5m/10s=0.5m／s，小华做功的功率P=FV=100N*0.5m／s =50W． 注意：1，每处错误及其修改均仅限一词； 2，只允许修改10处，多者（从第11处起）不计分Dear Mary,I receive your E-mail just now. Don’t worry about me. I’m getting on well with my research work in the lab. But to my greatly surprise you say you will give up learn English. The reason is because you have not done well in it recently and you have lost interests. I’m afraid I couldn’t agree with you . I know it is difficulty to learn English, and English is widely used in the world today. It will be important tool in our future work. Beside, it is becoming more and more important in our daily life. If you study hard, you will be succeed. Do remember that where there is a will, there is a way. I’ m looking forward to hearing good news from you.Yours, Li Hua