（1）由题可知：Ek-fh-mgh=2mgh ·········① 小球的动能是势能的两倍
Ek-2fH+fh-mgh=1/2mgh ···········② 小球的动能是势能的一半
Ek=fH+mgH······················③ 能量守恒,最高点是动能完全转换为重力势能和内能
把③式分别代入①式②式化简后得fH+mgH-fh=3mgh············④
-fH+mgH+fh=3/2mgh········⑤
④＋⑤得2mgH=9/2mgh
解得h=4/9H··············⑥
（2）⑥代入④得fH+mgH-4/9fH=4/3mgH
解得f=3/5mg·········⑦
（3）⑦代入③得Ek=3/5mgH+mgH=8/5mgH