If indeed the friction coefficient is independent of surface area, then when I tilt them they should start to slide roughly at the same Angle.
若摩擦系数真的，与接触面积没有关系，那么两者下滑时的角度，应该基本相当。
2
Can start the flow of contacts and dynamic friction resistance is to minimize the friction resistance, it can save energy, easy to get a higher velocity.