（2）S=74.8m

23.（1）

22．   3    ，  1350   

14.D  15.AC  16.AD  17.A   18.C  19.A  20.D  21.ABC

31． (1)                                                                     

(2)                                  (3)                                             

(4)                     (5)                     (6)                                      

(7)                                                                                   

物理答案

30． (1)                                          (2)                                     

(3)                                                                                

(4)实验步骤：

                                                                                     ；

                                                                                     ；

实验结果和相关结论：

                                                                                     ；

                                                                                     ；

                                                                                     。

29．（15分）Ⅰ（1）                 、                    ；（2）                     ；

Ⅱ（1）                                                                        ；

（2）                                        ；                                        ；

（3）①                                                  ；②                         ；

（4）                                                               。

28．（12分）（1）     ；        ；（2）      ；      ；（3）               ；（4）              。

27．（17分）（1）             ；                                                          。

（2）                                                                ；（3）                  ；

(4)                 ；（5）                                                                 ；

（6）                ；                       ；

（7）              ；                                                                  。

26．（共16分（1）                                    ；                                  。

（2）                   ；（3）                           ；                          。

（4）                                                                    ；

                                 ；                                               。

（5）                 。