Question

An athlete completes one round of a circular round of a circular track of diameter 200m in 40s. What will be the distance covered and the displacement at the end of 2 mins 20s? With steps plse..

Answer 1

distance covered in one complete round ie., 40 sec.
   = circumference of circle of diameter 200 m
   =  π 200  meters.
Distance covered in 2 mins 20 sec or 140 sec: =  200 π * 140/40 = 700 π meters

In 140 seconds, the athlete makes 3 complete rounds and runs for 20 secs after that.

in 40 secs, he runs a complete circle (covers 360°).  So in 20 secs, athlete runs half-circle and covers 180°.

So at the end of 140 seconds, athlete is at the diametrically opposite end on the circular track. 

The displacement = vector joining the initial position to the final position.
  It magnitude = diameter = 200 meters.

Answer 2

Answer:

Given :-

Diameter of circular track = 200 m

Radius, r = 200/2 = 100 m

Time taken by athlete to complete one round = 40 seconds.

To Find :-

Distance covered = ??

Displacement = ??

Formula to be used :-

Speed = Distance/Time

Circumference of circle = 2πr

Solution :-

2 min 20 seconds = 140 seconds

Number of rounds = 140/4 = 35

⇒ Distance covered = 35 × circumference

⇒ Distance covered = 35 × 2 × 22/7 × 100

⇒ Distance covered = 5 × 2 × 22 × 100

⇒ Distance covered = 22000 m

Hence, the distance covered at the end of 2 min 20 seconds is 22000 m or 22 km.

And displacement is 200 m as it return to initial position again.