What is the runner's displacement from his starting point?

Question

A runner, jogging alone a straight-line path, starts at a position 60.0 m east of a milestone marker and heads west. After a short time interval he is 36.0 m west of the mile marker. Choose east to be the positive x-direction.

Answer 1

So Displacement is a vector quantity which has magnitude and direction.

The displacement in this question is a vector from the starting point to the end point.

You can place two points on a graph (x-axis since it's from east to west) and the direction points from (60.0, 0.0) [60.0 m east of the milestone marker which we can make (0.0,0.0)] to (-36.0,0) [36.0 m west of the milestone marker] And note that east is positive which means west is negative.

Displacement in the x direction = final - initial = -36.0 - 60.0 = -96.0 m

Displacement in the y direction = final - initial = 0.0 - 0.0 = 0.0 m

[In this case, there's no y direction but if there are, make sure to take it into account and use pythagorean theorem to solve it]

Answer: Displacement = -96.0 meters