Displacement is the distance traveled in a specific direction. From this definition, we can see that displacement is a vector quantity that has magnitude and direction.
So;
For the first day, the person walks 4km East:
4km
Start ----------------------------→ first day
7km
← ------------------------------------------------------ Second day
The displacement of the boy = 7km - 4km = 3km due West
As given, the student has three balloons and rubs two of them on a piece of wool. The rubbing of balloon on wool is the independent variable as it was done on two and not on the third as control.
