Dear student,



Dear student,

Here is an example to understand the difference between distance and displacement.

Difference between distance and displacement

To test your understanding of this distinction, consider the motion depicted in the diagram below. A student of physics walks 9 meters east, 5 meters south, 9 meters west, and finally 5 meters north.

[pic]

Fig 1.1

Even though the physics student has walked a total distance of 28 meters, his displacement is 0 meters. During the course of his motion, he has "covered 28 meters of ground" (distance = 28 m). Yet when he is finished walking, he is not "out of place" - i.e., there is no displacement for his motion (displacement = 0 m). Displacement, being a vector quantity, must give attention to direction. The 9 meters east cancels the 9 meters west; and the 5 meters south cancels the 5 meters north. Vector quantities such as displacement are direction aware. Scalar quantities such as distance are ignorant of direction. In determining the overall distance traveled by the physics student, the various directions of motion can be ignored.

Another example of distance and displacement is illustrated in Figure 1.2

[pic]

Fig 1.2

Saleh (A physics student) walks from the point A to B to C. What does the distance he travel? What is the displacement? Let’s calculate first the distance that john travels. While calculating distance, we look at the numeric value of interval between travelled points. As you can see from Figure 1.2 he travels from A to B to C. Distance from A to B is 4m and B to C is 3 m. Their sum will give us total distance;

4+3=7

Then it's time to calculate displacement. As I mentioned before displacement is a vector quantity. Thus, it must have both magnitude and direction. In this example our initial point is A, and our final point is C. Displacement vector is an internal between the initial and final points. As it clearly seen in the Figure1.2 interval between A to C is 5m. So, our displacement vector is 5m and its direction is from the point A to C.

Regards

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