力的三要素内容是什么?物体保持静止的条件是什么?
参考答案:
按题意分述如下。
(1)力的三要素是指力的大小、方向和作用点。
(2)物体静止的条件是合力等于零,合力矩等于零。
The plan was in ______ just because people were unwilling to cooperate.[ ]
A. ruins
B. pieces
C. danger
D. trouble
A.I= ,从上向下
B.I= ,从上向下
C.I= ,从下向上
D.I= ,从下向上