[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/43cxgZLj.png
I am a highschool student and i was  studying kineamtics about position of a body so one thing i do not understand in this diagram is the  position of woman initally at t=0 this women was at x=1.5m from refrence frame but if we look at the hands of the women or the leg of the women or any point of the women is at different position so how we can say that this women is at x=1.5m. how we can define the position of the woman?