A:40°
B:50°
C:60°
D:75°
It's rather windy today. Put on some warm clothes, _________ you'll catch a cold.
秒____ 爱____ 江____ 喳____
妙____ 受____ 汇____ 查____
如图所示,汽车过拱形桥时的运动可以看做匀速圆周运动,质量为1吨的汽车以20m/s的速度过桥,桥面的圆弧半径为500m,g取9.8m/s2,则汽车过桥面顶点时对桥面的压力是( )