Question

an athlete completes one round of a circular track of a diameter 49m in 20 s. calculate the distance travelled and displacement at the end of 30 seconds

Answer 1

Solution:-
Diameter=49m
So,radius=49/2m

Time =20s
Distance travelled=circumference of circle=
$2 \times \pi \times r$
Therefore,
$distance = 2 \times \frac{22}{7} \times \frac{49}{2} \\ = > 154$

Hence,he travelled 154m

Now,
Time taken to complete one round=20seconds
So,total Distance complete in 30 sec=
$= > \frac{30}{20} \\ = > 1.5$
Since ,in 30 sec one and half of the circle is completed so the displacement will be the shortest distance between initial and final position.

After 30seconds he will be opposite side of the starting point.

Here,The shortest distance is= diameter of circle which is= 49m.

Hence,
Distance covered in 20 seconds =154m
Displacement covered in 30 seconds=49m