（1）小球落在
处时，
············································· 2分
·································································· 2分
小球从
到
···················································································· 2分
··················································· 2分
（2）小球从
到
由动能定理得；
·········································································· 3分
······································································ 2分
（3）小球从
到地，机械能守恒得：
······································································· 3分
······································································ 2分
（其他正确解法同样得分）
，与水平长木板间的动摩擦因数为
，长木板
长为
，距离水平地面的高度为
，斜面倾角为
、
、
两点间竖直高度为
。求：
的水平距离
；
的大小；
的小。