work done=0?

Since [work done] = force x displacement (in the direction of force)

thus in order to have a non-zero work-done, both the [force] and the [displacement] must not be zero.

In the situation that the [froce] and [displacement] are perpendicular to one another, it is clearly that the [displacement] of the object is NOT due to the action of the concerned [force] (in that case, it is due to the action of other forces). The force in question has no displacement of its own, and obviously does no work.

[Note: the transfer of energy in such situation is due to work done by other forces, not by the concerned force]

其實呢,E一個問題同向量有關,

你知LA, u∙v=∣u∣∣v∣cosθ

兩個互相perpendicular相PRODUCT==F1∙F1=∣F1∣∣F2∣cos90=0,,

AND , W=F∙s=∣F∣∣s∣cosθ

if F and d are perpendicular , then W=F∙s=∣F∣∣s∣cos90=0...

2008-06-09 16:47:24 補充：
∣ 係∣

2008-06-09 16:47:51 補充：
∣ 係 absolutely value