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

 -Shresthi Goyal, Subject Matter Expert at Edumarz 

Answer:

If diameter is 200m, then radius is 200/2 m, that is, 100 m.

 Total time taken = 2 minutes 20 seconds

 1 minute = 60 seconds

2 minutes = 120 seconds

2minutes 20 seconds =  120 +20 = 140 seconds.

One round is completed in 40 seconds.

  So, number of rounds =  140/40 =  3.5 rounds 

The distance covered in 140 seconds =  2πr × 3.5

(Since,  1  round =  Circumference of  Circle) 

Distance covered  = 2πr × 3.5

= 2X 22/7  X 100 X 3.5  = 2200m

1 round = 2πr = 2×22/7× 100

 Therefore, for 3 rounds, displacement is zero.

For 0.5 round, it will be equal to the diameter.

Therefore, displacement will be 200m