讲解一下这个题目---**Extraction Content:** **Question Stem:** 例2: 用轻质细线把两个质量未知的小球悬挂起来, 如图1—2所示, 今对小球a持续施加一个向左偏下30°的恒力, 并对小球b持续施加一个向右偏上30°的同样大小的恒力, 最后达到平衡, 表示平衡状态的图可能是 ( ) **Initial Diagram Description:** * **Type:** Diagram showing two masses suspended by strings. * **Main Elements:** * **Suspension Point:** A horizontal bar representing the suspension point at the top. * **Strings:** Two strings. The upper string is vertical and attached to the suspension point and ball 'a'. The lower string is attached to ball 'a' and ball 'b'. * **Points:** Two solid circles representing small balls, labeled 'a' and 'b'. Ball 'a' is above ball 'b'. * **Labels:** 'a' and 'b' next to the respective balls. "左" (Left) and "右" (Right) below ball 'a' and 'b' respectively, indicating direction. "图1—2" at the bottom left. * **Relative Position:** Ball 'a' is directly below the suspension point. Ball 'b' is directly below ball 'a'. Both strings appear vertical in this initial configuration. **Options:** **(A)** * **Description:** Diagram showing two masses suspended by strings in a different configuration. * **Main Elements:** * **Suspension Point:** A horizontal bar at the top. * **Strings:** Two strings. The upper string is attached to the suspension point and ball 'a'. The lower string is attached to ball 'a' and ball 'b'. * **Points:** Two solid circles representing balls, labeled 'a' and 'b'. Ball 'a' is to the left of a vertical dashed line from the suspension point. Ball 'b' is to the right of the vertical dashed line and to the right and slightly below ball 'a'. * **Lines:** A vertical dashed line extends downwards from the suspension point. The upper string is angled to the left from the vertical. The lower string is angled downwards and to the right from ball 'a' to ball 'b'. * **Label:** '(A)' below the diagram. **(B)** * **Description:** Diagram showing two masses suspended by strings in a different configuration. * **Main Elements:** * **Suspension Point:** A horizontal bar at the top. * **Strings:** Two strings. The upper string is attached to the suspension point and ball 'a'. The lower string is attached to ball 'a' and ball 'b'. * **Points:** Two solid circles representing balls, labeled 'a' and 'b'. Ball 'a' is to the left of a vertical dashed line from the suspension point. Ball 'b' is to the right of the vertical dashed line and to the right and slightly below ball 'a'. * **Lines:** A vertical dashed line extends downwards from the suspension point. The upper string is angled to the left from the vertical. The lower string is angled downwards and to the right from ball 'a' to ball 'b'. The configuration of the strings and balls is visually similar to option (A). * **Label:** '(B)' below the diagram. **(C)** * **Description:** Diagram showing two masses suspended by strings in a different configuration. * **Main Elements:** * **Suspension Point:** A horizontal bar at the top. * **Strings:** Two strings. The upper string is attached to the suspension point and ball 'a'. The lower string is attached to ball 'a' and ball 'b'. * **Points:** Two solid circles representing balls, labeled 'a' and 'b'. Ball 'a' is to the left of a vertical dashed line from the suspension point. Ball 'b' is to the left of the vertical dashed line and to the right and below ball 'a'. * **Lines:** A vertical dashed line extends downwards from the suspension point. The upper string is angled to the left from the vertical. The lower string is angled downwards and to the right from ball 'a' to ball 'b'. * **Label:** '(C)' below the diagram. **(D)** * **Description:** Diagram showing two masses suspended by strings in a different configuration. * **Main Elements:** * **Suspension Point:** A horizontal bar at the top. * **Strings:** Two strings. The upper string is attached to the suspension point and ball 'a'. The lower string is attached to ball 'a' and ball 'b'. * **Points:** Two solid circles representing balls, labeled 'a' and 'b'. Ball 'a' is to the left of a vertical dashed line from the suspension point. Ball 'b' is to the left of the vertical dashed line and to the left and below ball 'a'. * **Lines:** A vertical dashed line extends downwards from the suspension point. The upper string is angled to the left from the vertical. The lower string is angled downwards and to the left from ball 'a' to ball 'b'. * **Label:** '(D)' below the diagram.