问题 计算题

(8分)如图所示,某工人重600N,站在水平面上,用100N的拉力向下匀速拉动绳子,提起一浸没在水中体积为1.2×10﹣2m3,重360N的物体.(物体始终浸没在水中,且忽略水对物体的阻力,ρ=1×103kg/m3,g=10N/kg)求:

(1)已知工人双脚与地面的总接触面积是3×10﹣2m2,工人没有拉动绳子时对地面的压强;

(2)物体浸没在水中时受到的浮力;

(3)提起物体时滑轮组的机械效率.

答案

(1);(2)120N;(3)80%

题目分析:(1)工人没有拉动绳子时对地面的压力等于人的重力600N,则人对地面的压强为:

(2)物体浸没在水中时,,根据阿基米德原理,物体受到的浮力为:

(3)

填空题

单词拼写(根据句意、首字母或中文提示用正确形式写出下列单词,

每空一词.提示:必须用必修五、选修六所学新单词.

1.His report was c__________(不断地) interrupted by applause.

2. Can you telephone me at your c_________ to arrange a meeting?

3. Destruction of the environment is one of the most serious ____________(挑战) we face.

4. Her father didn't a_____________ of her marriage to him, which made her very sad.

5. The teacher and his students are d_________ (高兴的)with the result of the experiment.

6. After some repeated a________, they finally succeeded in winning the competition.

7. Is now an a_________(适当的)time to call on Professor Simpson? ?

8. The washing machine is fully __________. (自动的)

9. The monitor gave a present to their headmaster on b_________ of all the students.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           10. He was a_____________ as captain of the English team.

单项选择题