displacement

冇個選得
(a)
No. For example, I take a taxi from my home to Mong Kok and then go back to my home. If I consider displacement, then the value is 0 and I don't need to pay the money and this should not be the case.
(b)
No. In this case, the distance and the displacement give the same value since the distance of jump should be positive.
(c)
No. For example, I want to make a plan in a hiking at starting point A and walking 3 hours in the trip, finally go back to point A. The important thing here is the distance of the path during the trip and not the displacement which is 0
(d)
No. For example I using the string to measure the circumference of the circle starting at point A, then after my string reach the point A again. The distance of the string (from starting point to end point) is equal to the circumference of the circle but the corresponding displacement is 0.
So, no case should displacement, but not distance ,be considered.


2007-01-22 15:27:00 補充：
不過(b)係可以用displacement, 其他3個用都唔用得不過(b)亦都不是should use displacement