一、重力场中单摆的特点1.构成如图1所示,长度为L摆长、不可伸长的轻绳下端悬挂一半径为r小球,且L摆长r,便可构成单摆.2.单摆的受力特点如图2所示,单摆摆动过程中,摆球始终会受竖直向下的重力和沿着细绳方向且指向悬点的拉力F T.3.单摆的周期 First, the characteristics of a single pendulum in the gravity field 1. Composition As shown in Figure 1, the length of the L length of the swing, the lower end of the non-elongated rope hanging a radius of r small ball, and L swing length  r, can form a single Pendulum .2 pendulum force characteristics shown in Figure 2, the pendulum swing process, the pendulum will always be subject to the vertical downward gravity and along the direction of the string and point to the hanging point of the tension F T.3. Single pendulum cycle