请用中文的演示视频帮我分析并讲解这道滑轮组题目，要简单清晰，有条理，易懂---以下是从图片中提取的全部内容，并以结构化纯文本格式输出： **Title:** 滑轮组计算 (Pulley System Calculation) **Section Header:** 一、计算题 (共 20 小题) (Calculation Problems (Total 20 questions)) **Question Stem:** 1. 如图甲所示是一种起重机的简图，为了保证起重机起重时不会翻倒，在起重机右边配有一个重物 G₀。已知 OA=12m，OB=4m，用它把重力为 2.3×10⁴N 的货物 G 匀速提起。求： **Sub-questions:** (1) 若起重机自重不计，吊起货物 G 时为使起重机不翻倒，右边的配重 G₀ 至少为多少牛？ (2) 如果起重机吊臂前端是由如图乙所示的滑轮组组成，动滑轮总重 1000N，绳重和摩擦不计，如果拉力的功率为 6kW，则把 2.3×10⁴N 的货物 G 匀速提高 20m，拉力 F 的大小是多少？需要多少时间？ **Diagram Description:** **Figure 甲 (Figure A):** * Type: Schematic diagram of a crane. * Main Elements: * A pivot point labeled O. * A weight labeled G suspended below point A on the left side of O. The distance OA is labeled as 12m. * A counterweight labeled G₀ suspended below point B on the right side of O. The distance OB is labeled as 4m. * A structural representation of the crane boom extending left from O and supporting G. * A vertical dashed line passing through O. * Labels: O, A, B, G, G₀. Distances OA=12, OB=4. * Relative Position: O is the pivot. G is to the left of O. G₀ is to the right of O. **Figure 乙 (Figure B):** * Type: Pulley system (block and tackle). * Main Elements: * A fixed pulley at the top, attached to a support structure. * Two movable pulleys below the fixed pulley, stacked vertically. * A rope passing around the pulleys. It starts from the fixed pulley, goes down around the top movable pulley, up to the support, down around the bottom movable pulley, and then upwards. The pulling force F is applied to the upward free end of the rope. * A load labeled Z is attached to the bottom movable pulley. This load Z represents the force lifting the cargo G in Figure A. * There are 4 segments of rope supporting the load Z and the movable pulleys. * Labels: F (pulling force), Z (load). * Relative Position: Fixed pulley above movable pulleys. Load Z attached below the bottom movable pulley. **Other Relevant Text:** * "求:" (Ask:) * "甲" (Label under Figure A) * "乙" (Label under Figure B - partially visible) * Handwritten note: "解 (1)" (Solution (1)) **Given Values/Data:** * OA = 12m * OB = 4m * Weight of cargo G = 2.3 × 10⁴ N * Total weight of movable pulleys (动滑轮总重) = 1000 N * Power of pulling force (拉力的功率) = 6 kW * Height to lift cargo G = 20m