解答这个题---```plain text
10. (14 分)(2023 • 北京卷, T9)
2022 年,我国阶段性建成并成功运行了“电磁炮”,创造了大量电磁推进技术的世
界最高速度记录。一种两级导轨式电磁推进的原理如图所示。两平行长直金属导轨固定在水平平面,导轨间垂直安放金属棒。金属棒可沿导轨无摩擦滑行,且始终与导轨接触良好,电流从一导轨流入,经过金属棒,再从另一导轨流回,图中电源未画出。导轨电流在两导轨间产生的磁场可视为匀强磁场,磁感应强度 B 与电流 i 的关系式为 B = ki (k 为常量)。金属棒被该磁场力推动。当金属棒由第一级区域进入第二级区域时,回路中的电流由 I 变为 2I。已知两导轨内侧间距为 L,每一级区域中金属棒被推出的距离均为 s,金属棒的质量为 m。求:
**Diagram Description:**
* Type: Schematic diagram of a two-stage electromagnetic railgun.
* Elements:
* Two parallel horizontal lines representing rails.
* A vertical bar between the rails represents the metal rod.
* The diagram is divided into two regions: "第一级区域" (First Stage Region) on the left and "第二级区域" (Second Stage Region) on the right.
* 'x' symbols within both regions indicate a magnetic field directed into the page.
* Labels indicate the current through the rod in each region: 'I' in the first region and '2I' in the second region.
* Magnetic flux density is indicated as B=ki, specifically B=kI in the first region (where current is I) and B=2kI in the second region (where current is 2I).
* The metal rod is labeled "金属棒".
* Arrows show the direction of current flow through the rod from left to right (I or 2I).
**Given Information:**
* Relationship between magnetic flux density B and current i: B = ki (k is a constant)
* Current in the first stage region: I
* Current in the second stage region: 2I
* Distance between inner sides of rails: L
* Distance pushed in each stage region: s
* Mass of the metal rod: m
**Question(s):**
The problem ends with "求:", indicating that specific quantities are to be calculated based on the given information. However, the specific questions are not visible in the provided image.
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Here is the extracted content from the image:
**Question Stem:**
(1) 金属棒经过第一级区域时受到安培力的大小 F₁。(4分)
(2) 金属棒经过第一、二级区域的加速度大小之比 a₁:a₂。(6分)
(3) 金属棒从静止开始经过两级区域推进后的速度 大小v。(4分)
**Other Relevant Text:**
(1) F=BIL
=kI²L
**Chart/Diagram Description:**
* **Type:** Diagram showing magnetic field lines.
* **Main Elements:**
* A central shaded circular/elliptical region.
* Several curved lines representing magnetic field lines originating from the central region, looping outwards, and returning to the central region. The lines are symmetrical.
* An arrow is shown on one of the field lines indicating its direction (outwards and looping back).
* Small lines radiate outwards from the central region, potentially indicating poles or a source.
**Note:** No options (A, B, C, D) are visible in the provided image for these questions. The drawing and the calculation "F=BIL =kI²L" appear in the image but their direct relation to the specific questions asked is not explicitly stated within the cropped section.