Magnitude of Displacement
Average velocity =
A girl moves along the boundary of a square field of side 20m in 80 secs.
Each side is 20m long.
So perimeter/ boundary is
That means she is moving
After 200 seconds she will have covered 200m.
The number of rounds covered along the complete boundary will be 200/ 80 = 2.5 rounds.
That means she is at the diagonally opposite point from where she started after 200 seconds.
So, the displacement will be given as distance between the initial position and final position, i.e diagonal of the square field. It will be hypotenuse of the right triangle with side =
Apply Pythagoras theorem,
Average velocity = Displacement/ total time taken
Magnitude of displacement
Magnitude of average velocity
Assuming that the girl is moving at a constant speed for the 200 seconds, she will get around the field
The displacement (notated by
If you look at my crappy diagram below, you can see that the girl starts at the bottom left corner and ends up at the top right X. The magnitude of the displacement is the distance of the straight line from start to end point and can be solved using the Pythagorean Theorem.
So, the displacement is
Now, the average velocity (
If we designated up the page as north, we could say that the average velocity and displacement both have directions of north-east.