jik=80.0;
komakazu=100.0;
em=100.0;
wr=10.0;
ww=1.0;
er=2.0;
enbshothe=0.0;
enbshoome=0.0;
enbkaithe=0.0;
g=9.8;
ktk=1.0;

dt=jik/komakazu;

waku=
	Graphics[
		{Line[{ {-wr,0.0},{-wr,-wr},{wr,-wr},{wr,0.0} }]
		,Circle[{0.0,0.0},wr,{Pi,2 Pi}]
		}
		,AspectRatio->Automatic
		,PlotRange->{{-wr,wr},{-wr,er}}
	];


enban[x_,y_,er_,kaithe_,xn_,xx_,yn_,yx_]:=
	Graphics[
		{
			{
			GrayLevel[0.0]
			,Disk[{x,y},er,{kaithe,kaithe+Pi/2}]
			}
			,{
			GrayLevel[0.5]
			,Disk[{x,y},er,{kaithe+Pi/2,kaithe+Pi}]
			}
			,{
			GrayLevel[0.0]
			,Disk[{x,y},er,{kaithe+Pi,kaithe+3 Pi/2}
			]
			}
			,{
			GrayLevel[0.5]
			,Disk[{x,y},er,{kaithe+3 Pi/2,kaithe+2 Pi}]
			}
		}
		,AspectRatio->Automatic
		,PlotRange->{{xn,xx},{yn,yx}}
	];

ey = NDSolve[
			{(wr-er) y''[u] == 4.0/5.0 g Sin[Pi/2 - y[u]]
							- ktk ww/em (wr-er)^2 y'[u]
			,y[0.0] ==enbshothe
			, y'[0.0]==enbshoome
			}
			,y
			,{u,0,jik}
			,MaxSteps->2000
		];

Manipulate[
	enbthe = N[ (y[t] /. ey)[[1]] ];
	enbkaithe= N[(wr/er-1) enbthe];
	Show[waku
		,enban[(wr-er) Cos[enbthe]
				,-(wr-er) Sin[enbthe]
				,er,enbkaithe,-wr,wr,-wr,er
		]
		,DisplayFunction->$DisplayFunction
	]
	,{t,0,jik,dt}
]