17.
(2022高二上·鞍山月考)
如图所示,绝缘水平面上固定有足够长的两平行金属导轨,导轨间的距离L=0.4m,金属导轨所在的平面与水平面夹角θ=
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsup%3E%3Cmrow%3E%3Cmn%3E37%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmtext%3Eo%3C%2Fmtext%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
, 在导轨所在平面内,分布着磁感应强度B=1.0T、方向垂直于导轨所在平面向上的匀强磁场。金属导轨的一端接有电动势E=6.0V、内阻r=1.0Ω的直流电源。现把一个质量m=0.1kg的导体棒ab放在金属导轨上,此时导体棒恰好静止。导体棒与金属导轨垂直且接触良好,导体棒与金属导轨接触的两点间的电阻R=2.0Ω,金属导轨电阻不计。最大静摩擦力与滑动摩擦力大小相等,sin
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsup%3E%3Cmrow%3E%3Cmn%3E37%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmtext%3Eo%3C%2Fmtext%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
=0.6,cos
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsup%3E%3Cmrow%3E%3Cmn%3E37%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmtext%3Eo%3C%2Fmtext%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
=0.8。取重力加速度大小g=10m/s
2 , 求:
![](//tikupic.21cnjy.com/2022/12/27/d6/21/d621d6dfaf09ac8506fae103a67d1a4a_300x175.png)