Similarity Principle and Dimension Analyse 3. Dynamic similarity a defination The forces of corresponding points of prototype and model are consistent in direction and in proportion to magnitude that is called dynamic similarit Density scale 8 =pn (47) Mass scale 5= p, V (48) pm/m Force scale OFF E="n=6n2=022(49) 1313 3. Dynamic similarity Density scale m n     = （4—7） Mass scale 3 l m m n n m n m V V m m      = = =  （4—8） Force scale 2 2 m a l m m n n m n F m a m a F F       = = = =   （4—9） The forces of corresponding points of prototype and model are consistent in direction and in proportion to magnitude that is called dynamic similarity . defination：