一、单选题1.用悬挂法测定不规则物体的重心依据的原理是:( )A.物体的重心总在物体内部.B.重力和悬挂线的拉力是一对作用力和反作用力.C.两力平衡时重力通过物体重心.D.物体所受重力作用可认为集中于重心,悬挂平衡时重力和悬线拉力平衡,悬线延长线通过重心.2.置于水平桌面的支架上吊一只装满细砂的漏斗,让漏斗左、右摆动,于是桌面上漏下许多砂子,经过一段时间形成一砂堆,砂堆的纵剖面最接近图1中哪一种形状?( ) First, single-choice questions 1. Use suspension method to determine the center of gravity of irregular objects based on the principle: () A. The object’s center of gravity is always inside the object. B. Gravity and suspension line pull is a pair of force and reaction force. C. Gravity passes through the object’s center of gravity when the two forces are balanced. D. The object’s gravity is considered to be centered on the center of gravity. When the balance is balanced, the gravity and the suspension line tension are balanced. The suspension line extends through the center of gravity. 2. The frame is placed on a horizontal table. A funnel filled with fine sand, allowing the funnel to swing left and right, so many sands were dropped on the tabletop. After a period of time, a sand pile was formed. The longitudinal profile of the sand pile was closest to which shape in Figure 1?