Question

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

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:

Answer:The distance covered at the end of 2 min 20 seconds is 2200 m or 22 km. And displacement is 200 m.

Explanation:

Given:-

• The diameter of the circular track = 200 m
• Radius (r) = 200/2 = 100 m
• Time is taken by an athlete to complete one round = 40 seconds.
• Displacement = ??

Total time athlete moves – 2 min 20 seconds

2 min 20 seconds = 2 × 60 + 20 = 140 seconds

Distance covered in one round

Distance covered in one round = Circumference of circle = 2πr

= 2 × 100π

=200π

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

Number of rounds completed in 140s = 140/40= 35

Distance covered = 3.5 × circumference

= 3.5 × 2πr

= 3.5 × 2 × 3.14 × 100

= 2200 m

The distance covered at the end of 2 min 20 seconds is 2200 m or 22 km.

Displacement is 200 m as it returns to the initial position.

@WildCat7083