解释一下这道题---**Extraction Content:** **Question Number:** 22. (12分) **Question Stem and Information:** 用滑轮组提升水中物体 A 的示意图。 当物体 A 完全在水面下被匀速提升的过程中，物体 A 所受浮力为 80N，小明对绳子竖直向下的拉力为 F₁, 水平地面对小明的支持力为 N₁。 当物体 A 有 1/2 的体积露出水面且静止时，小明对绳子竖直向下的拉力为 F₂，水平地面对小明的支持力为 N₂。 已知动滑轮所受重力为 120N，小明所受重力为 600N，N₁ : N₂ = 13 : 12。 不计绳重、滑轮与轴的摩擦以及水的阻力。 **Questions:** 则物体 A 所受重力为多少 N? 若小明脚与地面接触面积为 320cm²，则 A 全部拉出水面小明对地面的压强? **Chart/Diagram Description:** * **Type:** Schematic diagram of a pulley system lifting an object from water. * **Main Elements:** * Pulley System: Consists of two fixed pulleys and one movable pulley. The fixed pulleys are attached to a horizontal support bar. The movable pulley is attached to the object A. * Object A: A rectangular block labeled "A", submerged in water initially. * Container: A container holding water, with object A inside. * Rope: A rope passes through the pulleys. One end is attached to the horizontal support bar, goes down around the movable pulley, up around a fixed pulley, horizontally across to another fixed pulley, and then goes vertically downwards, being pulled by a figure representing "小明" (Xiaoming, implied to be the person pulling the rope). The figure is not explicitly drawn, but the context implies someone is pulling the rope. * Support: A horizontal bar supports the fixed pulleys. * **Labels:** The object is labeled "A". * **Relative Position and Direction:** The object A is shown partially submerged in the water in the container. The rope is arranged in a specific way around the pulleys for lifting. The force F₁ and F₂ are the downward pulls by Xiaoming on the rope. N₁ and N₂ are the upward support forces from the ground on Xiaoming.