1、选择题  现有一绕太阳做圆周运动的行星，质量是地球质量的2倍，轨道半径也是地球轨道半径的2倍，那么下列说法中正确的是（　　）

A．由F=style="shiti/data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABoAAAAnCAIAAACezM/qAAABPUlEQVRIie2Vva1DIQyFvQVjUDAEU7hhhwzhxiMwAw0TZIXbeAO28Cu4cEmUPwUiRXpxBUh8OjYHG3RpwJfgxAEAgLGhzOMYUVRVS7DGIc+r20MSjwJncWXLdiFOEnOSvp3EFaI47qdwjD5v48MqtCd3osro6kISAwAn6YaoGY2FZ3T1sGw5tnyrOvE2RAqckgMTU/TImUKgXDMK1rS1RqKiJVgDRzgZ1Kkk9ognymXLBozHU7lEZArNXELt8GZAlV1TyBQATN6Kqrh9oWOOzb2PcMdNRlcVXZmzmut86YnbuMGH4loVOrfjDMD4me7iesklcbuwV7prubL+42RXxv/CLYwPqPvhfrhZXO1LtaFmCmMTfwenqn2MeMRXetQTXB8jzziv4foYWYI72v0C3NDuV+D6nF+DeyO+G/cHgDnAHipgLvEAAAAASUVORK5CYII=" alt="">可知，行星所需向心力与地球所需的向心力相同

B．由v=ωr可知，行星的线速度是地球线速度的2倍

C．由style="shiti/data:image/png;base64,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" alt="">=style="shiti/data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABoAAAAnCAIAAACezM/qAAABPUlEQVRIie2Vva1DIQyFvQVjUDAEU7hhhwzhxiMwAw0TZIXbeAO28Cu4cEmUPwUiRXpxBUh8OjYHG3RpwJfgxAEAgLGhzOMYUVRVS7DGIc+r20MSjwJncWXLdiFOEnOSvp3EFaI47qdwjD5v48MqtCd3osro6kISAwAn6YaoGY2FZ3T1sGw5tnyrOvE2RAqckgMTU/TImUKgXDMK1rS1RqKiJVgDRzgZ1Kkk9ognymXLBozHU7lEZArNXELt8GZAlV1TyBQATN6Kqrh9oWOOzb2PcMdNRlcVXZmzmut86YnbuMGH4loVOrfjDMD4me7iesklcbuwV7prubL+42RXxv/CLYwPqPvhfrhZXO1LtaFmCmMTfwenqn2MeMRXetQTXB8jzziv4foYWYI72v0C3NDuV+D6nF+DeyO+G/cHgDnAHipgLvEAAAAASUVORK5CYII=" alt="">可知，行星的线速度是地球线速度 倍

D．由style="shiti/data:image/png;base64,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" alt="">= ma，行星的向心加速度是地球向心加速度的

2、选择题  汽车在水平路面上转弯时，向心力是
A.重力和支持力的合力
B.滑动摩擦力
C.静摩擦力
D.重力、支持力、牵引力的合力

3、简答题  如图所示，在直角坐标系的第一、四象限内有垂直于纸面的匀强磁场，第二、三象限内有沿x轴正方向的匀强电场，电场强度大小为E，y轴为磁场和电场的理想边界．一个质量为m，电荷量为e的质子经过x轴上A点时速度大小为v0，速度方向与x轴负方向夹角为θ=30°．质子第一次到达y轴时速度方向与y轴垂直，第三次到达y轴的位置用B点表示，图中未画出．已知OA=L．
（1）求磁感应强度大小和方向；
（2）求质子从A点运动至B点时间．

4、计算题  如图所示，轻杆长2L，中点装在水平轴O点，两端分别固定着小球A和B，A、B球质量分别为m、2m，整个装置在竖直平面内做圆周运动，当杆绕O转动到某一时刻，A球到达最高点，此时球A与杆之间恰好无相互作用力，求此时O轴所受力的大小和方向。

5、选择题  如图所示，当汽车通过拱桥顶点的速度为10m/s时，车对桥顶的压力为车重的