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如图,直角坐标系\(xOy\)位于同一竖直平面内,其中\(x\)轴水平、\(y\)轴竖直\(.xOy\)平面内长方形区域\(OABC\)内有方向垂直\(OA\)的匀强电场,\(OA\)的长为\(l\)、与\(x\)轴间的夹角\(θ=30^{\circ}.\)一质量为\(m\)、电荷量为\(q\)的带正电小球\((\)可看作质点\()\)从\(y\)轴上的\(P\)点沿\(x\)轴方向以一定速度射出,恰好从\(OA\)的中点\(M\)垂直\(OA\)进入电场区域\(.\)已知重力加速度为\(g\).
\((1)\)求\(P\)的纵坐标\(y_{p}\)及小球从\(P\)射出时的速度\(v_{0}\);
\((2)\)已知电场强度的大小为\(E= \dfrac { \sqrt {3}mg}{2q}\),若小球不能从\(BC\)边界离开电场,\(OC\)长度应满足什么条件?