Statics:Bodies at rest or moving with uniform velocity （静态）
Dynamics:Bodies accelerating （动态）
Strength of materials:deformation of bodies under forces. （材料力学） Structural mechanics:focus on behavior of structures under loads. 结构力学
Structural mechanics deals with forces and motions of structural systems,it is necessary to study
the forces,the motions,and the relation between them.
it is an extension in application of mechanics of origin and deformable bodies.
