题目

Food festivals around the world Stilton Cheese Rolling May Day is a traditional day for celebrations，but the 2,000 English villagers of Stilton must be the only people in the world who include cheese rolling in their annual plans.Teams of four，dressed in a variety of strange and funny clothes，roll a complete cheese along a 50­metre course.On the way，they must not kick or throw their cheese，or go into their competitors' lane(赛道)．Competition is fierce and the chief prize is a complete Stilton cheese weighing about four kilos (disappointingly，but understandably the ch小丽同学利用如图所示的装置做“研究动能大小与速度大小的关系”的实验，她使用同一小球A，通过改变________来改变小球A到达水平面时速度的大小，通过比较木块B__________来比较小球动能的大小。