1．如图1所示，将木块放在粗糙程度相同的水平桌面，小华沿直线水平匀速拉动木块，在木块运动过程中                                                   (　　)

23．(8分)

   (1)                                                                      

   (2)

 (3)

  22．(8分)

   (1)                  

   (2)如图

   (3)                           

   (4)                    

  21．(8分)

   (1)                                                                                          

(2)                                                                                  

  20．(7分)

   解：(1)

     (2)

    (3)

六、综合能力题(本大题3小题，共24分)

  19．(8分)

   解：(1)

   (2)

   (3)

五、计算题(本大题2小题，共15分)

 18．(1)①                             ②                   ③               

     (2)                            

     (3)                            

     (4)                            

17．(1)                   

(3)                                                          

(4)