帮我解答这个题，我是初学者，请你讲解的仔细一些---**Diagram Description:** * **Type:** Schematic diagram illustrating a physics problem setup. * **Elements:** * Two parallel straight lines representing smooth metal rails, inclined upwards from left to right. * Two horizontal lines perpendicular to the rails, representing metal rods labeled 'a' and 'b'. Rods 'a' and 'b' are placed on the rails. * The distance between the parallel rails is labeled 'L'. * The plane formed by the rails is inclined at an angle $\theta$ to the horizontal (indicated by a dashed line). There are two labels of angle $\theta$, one below the rail plane and one above the horizontal line relative to the rail plane. * An arrow labeled 'B' pointing upwards and to the right, representing the magnetic field vector. This arrow is described as perpendicular to the plane of the rails and directed upwards along the incline. * A dashed line parallel to the horizontal reference line indicates the angle $\theta$ between the rail plane and the horizontal. **Textual Information:** 如图, 两根足够长的光滑金属直导轨平行放置, 导轨间距为 $L$, 两导轨及其所构成的平面均与水平面成 $\theta$ 角, 整个装置处于垂直于导轨平面斜向上的匀强磁场中, 磁感应强度大小为 $B$。现将质量均为 $m$ 的金属棒 $a$、$b$ 垂直导轨放置, 每根金属棒接入导轨之间的电阻均为 $R$。运动过程中金属棒与导轨始终垂直且接触良好, 金属棒始终未滑出导轨, 导轨电阻忽略不计, 重力加速度为 $g$。 (1) 先保持棒 $b$ 静止, 将棒 $a$ 由静止释放, 求棒 $a$ 匀速运动时的速度大小 $v_0$; (2) 在 (1) 问中, 当棒 $a$ 匀速运动时, 再将棒 $b$ 由静止释放, 求释放瞬间棒 $b$ 的加速度大小 $a_0$; (3) 在 (2) 问中, 从棒 $b$ 释放瞬间开始计时, 经过时间 $t_0$, 两棒恰好达到相同的速度 $v$, 求速度 $v$ 的大小, 以及时间 $t_0$ 内棒 $a$ 相对于棒 $b$ 运动的距离 $\Delta x$。