Physics A Level
Chapter 1: Kinematics 1.2 Distance and displacement, scalar and vector
Physics A Level
Chapter 1: Kinematics 1.2 Distance and displacement, scalar and vector
In physics, we are often concerned with the distance moved by an object in a particular direction. This is called its displacement.
Figure 1.8 illustrates the difference between distance and displacement. It shows the route followed by walkers as they went from town A to town C.
this example, the walkers travel a distance of $15 km$, but their displacement is only $10 km$, because this
.is the distance from the start to the finish of their walk
Their winding route took them through town B, so that they covered a total distance of $15 km$. However, their displacement was much less than this. Their finishing position was just $10 km$ from where they started. To give a complete statement of their displacement, we need to give both distance and direction:
displacement = $10 km$ at ${030^ \circ }$ or ${30^ \circ }$ E of N
Displacement is an example of a vector quantity. A vector quantity has both magnitude (size) and direction. Distance, on the other hand, is a scalar quantity. Scalar quantities have magnitude only.