如图，半径为$\sqrt{3}$cm的⊙O从斜坡上的A点处沿斜坡滚动到平地上的C点处，已知∠ABC=120°，AB=10cm，BC=20cm，那么圆心O运动所经过的路径长度为

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                                                                                                           宿山寺
                                                                                             众岫耸寒色，精庐向此分。
                                                                                             流星透疏水，走月逆行云。
                                                                                             绝顶人来少，高松鹤不群。
                                                                                             一僧年八十，世事未曾闻。