The position-time graph for a particle moving along a straight line is shown in figure. The total distance travelled by it in time $t=0$ to $t=10s$ is
(A). zero
(B). $10m$
(C). $20m$
(D). $30m$

Hint: The following graph shows the motion of a particle in a straight line using distance and time. The total distance travelled by the particle will be the sum of distances travelled in all the time intervals. The line parallel to the x-axis depicts that the particle does not change position.

Complete answer:
Distance is a scalar quantity and its magnitude is represented by its unit. Its SI unit is metres (m).
Given that the distance of a particle changes with time and its motion is depicted by the following position time graph.
The particle travels in a straight line.

Here, the position of the particle is the dependent quantity and time is the independent quantity.
According to the graph, the particle travels $10m$ in the first $2s$. After that, for time; $8-2=6s$ the particle remains at the same position. Then in the next $10-8=2s$, it travels another $10m$ back to its original position at $x=0$. Therefore, the total distance travelled by the particle will be-
$10m+10m=20m$
Therefore, the total distance travelled by the particle is $20m$.

Hence, the correct option is (C).

Note:
For the motion of particles depicted in the above graph, the displacement is zero. Displacement is a vector quantity. The independent quantity is taken along the x-axis and the dependent quantity is taken along the y-axis. When the particle is stationary or at rest, the graph is a straight line parallel to the x-axis. The ratio of distance to time is called velocity, which is the distance travelled per second.