High Quality Content by WIKIPEDIA articles! A virtual displacement delta mathbf {r}_i "is an assumed infinitesimal change of system coordinates occurring while time is held constant. It is called virtual rather than real since no actual displacement can take place without the passage of time.":263 In modern terminology virtual displacement is a tangent vector to the manifold representing the constraints at a fixed time. Unlike regular displacement which arises from differentiating with respect to time parameter t along the path of the motion (thus pointing in the direction of the motion), virtual displacement arises from differentiating with respect to the parameter ? enumerating paths of the motion variated in a manner consistent with the constraints (thus pointing at a fixed time in the direction tangent to the constraining manifold). The symbol ? is traditionally used to denote the corresponding derivative textstyle{partialover{partialepsilon}}big|_{epsilon=0}.

Данное издание не является оригинальным. Книга печатается по технологии принт-он-деманд после получения заказа.