论文部分内容阅读
一、选择题1.下列关于摩擦力的说法正确的是A.摩擦力的大小与正压力成正比B.摩擦力的方向一定与物体运动方向相反C.摩擦力一定是阻力2D..用运三动的根物轻体绳可将能质受到静摩擦力量为m的物块悬挂在空中,如图所示。已知ac和bc与竖直方向的夹角分别为30°和60°,则ac绳和bc绳中
First, multiple-choice questions 1. The following statements about friction are correct. A. The size of friction is proportional to positive pressure. B. The direction of friction must be opposite to the direction of motion of the object. C. The friction must be resistance 2D. The three-acting root light rope can suspend the mass in the air with a static friction force of m, as shown in the figure. Knowing that the angle between ac and bc and the vertical direction is 30° and 60°, respectively, then the ac and bc ropes