請寫出如圖18所示的幾個實驗所揭示的物理道理：

甲：                                                                     

乙：                                                                     

丙：                                                                     

�。�                                                                     

請寫出如圖18所示的幾個實驗所揭示的物理道理：

甲：                                                                     
乙：                                                                     
丙：                                                                     
�。�                                                                     

請寫出如圖18所示的幾個實驗所揭示的物理道理：

甲：                                                                     

乙：                                                                      

丙：                                                                     

�。�