（12分）游乐场的过山车可以底朝上在圆轨道上运行，游客却不会掉下来（如图甲）。我们可以把它抽象成图乙所示的由曲面轨道和圆轨道平滑连接的模型（不计摩擦和空气阻力）。若质量为m的小球从曲面轨道上的P点由静止开始下滑，并且可以顺利通过半径为R的圆轨道的最高点A。已知P点与B点的高度差h=3R，求：

（1）小球通过最低点B时速度有多大？

（2）小球通过B点时受到圆轨道支持力有多大？

（3）若小球在运动中需要考虑摩擦和空气阻力，当小球从P点由静止开始下滑，且刚好通过最高点A，则小球从P点运动到A点的过程中克服摩擦和空气阻力所做的功为多少？

小题1:We make         (玩具)in the factory for children from 1 to 5 years old.

小题2:Mr. Wang enjoys r         newspapers in the morning.

小题3:He is a police man .It’s a             (危险的) job.

小题4:I think giraffes are good-looking, but lions are u__________ .

小题5: There is much ________ （雨）here in summer.

小题6:My mother is l_________ on the beach.

小题7:What s_________ skirt would Joe like?

小题8:He is from France. He speaks F________ .  

小题9:The park near my home is very d_________（脏）, I don’t like to go there.

小题10:There are three            (小偷)in the police station.