Question

A car moves on a circular track of radius 7/22 km. After its start, when its displacement becomes zero for the first time, the distance covered by the car is

Answer 1

This could be simply solved by the concept of displacement. Also, displacement over a circular path is zero as initial and final positions are the same. Here, we will use the basic formula:
Perimeter of circle,
$P = 2\pi r$
Here, $P$ is the perimeter of the circle.
$r$ is the radius of the circle.

Complete step by step answer
We already know that the displacement of the car is zero,
Displacement of the moving car on a circular track equals zero when the car completes one complete circle. So, for the first-time displacement it becomes zero when it completes one full circle.
The car moves on a circular track.
So, its displacement becomes 0 for the first time when it completes one full round on the track.
The distance travelled will be the perimeter of the circular road.
$P = 2\pi r$
$P = 2 \times \pi \times \dfrac{7}{{22}} = 2Km$
Hence, the distance travelled by the car is 2 Km.

Note
There are three mathematical quantities that will be of primary interest to us as we analyse the motion of objects in circles. These three quantities are speed, acceleration and force. In physics, circular motion is a movement of an object along the circumference of a circle or rotation along a circular path. It can be uniform, with constant angular rate of rotation and constant speed, or non-uniform with a changing rate of rotation. Never forget to take the acceleration as the net acceleration before putting it to the equation. We can assume the example, if a body moves along a circle of radius r and covers half the circumference, then displacement is given by $s = 2r$ . In one-dimensional motion displacement of the object will be the shortest distance between final and initial point.