求出对应的物理量F的大小,要求动画简洁，鲜明。---**Chart/Diagram Description:** * **Type:** Physics system diagram / Force diagram. * **Main Elements:** * **Vertical Wall:** A vertical blue line on the left side, with red diagonal hatching indicating a fixed, rigid surface. * **Horizontal Surface:** A horizontal blue line at the bottom, with red diagonal hatching below it, indicating a rough ground or table surface. * **Pulley:** A blue circular shape with a black outline and a black dot at its center, positioned to the left of the blocks. A black line connects the pulley to the vertical wall, indicating it is fixed. * **Rope/String:** A blue line extends horizontally from the pulley to the right, connecting to Block A. * **Block A:** A gray rectangular block positioned on top of Block B. It is labeled 'A' in blue. Its mass is indicated as '3m' in red text above it. * **Block B:** A yellow rectangular block positioned below Block A, resting on the horizontal surface. It is labeled 'B' in blue. Its mass is indicated as '4m' in red text below Block A (implying it's B's mass). * **Friction Coefficients:** The symbol 'μ' (mu) in black text is present in two locations: * Between Block A and Block B, indicating the coefficient of friction for that interface. * Below Block B and above the horizontal surface, indicating the coefficient of friction for that interface. * **Applied Force F:** A black arrow pointing to the right, originating from the right side of Block B. It is labeled 'F=?' in blue, indicating an unknown force being applied to Block B. * **Arrows:** * A black arrow points from the pulley towards Block B, indicating an interaction or system involvement of Block B with the pulley system. * The rope (blue line) connects the pulley to Block A, implying tension acts on A to the left. * **Relative Position:** The pulley is fixed to the left wall. Block A is placed on top of Block B. Block B is resting on the horizontal rough surface. **Other Relevant Text:** * **Mass of Block A:** 3m * **Mass of Block B:** 4m * **Friction coefficient:** μ (between A and B, and between B and the horizontal surface) **Question Stem:** * 求F大小 (Qiú F dàxiǎo) * **Translation:** Find the magnitude of F.