Question

an althlets completes one round of a circular track of diameter 200m in 40sec .what will be the distance covered and the displacement al the end of 2min and 20 sec

Answer 1

Time=2 min 40 s=140 s
no.of rounds completed in 140s=(140/40)=3.5
distance traveled=3.5 * circumference of circle
3.5*2πr=3.5*22/7*200=2200m
The athlete completes 3.5 rounds of the circle. The displacement after 3 rounds will become zero as the athlete has reached its initial position. So the 0.5 round is the diameter traveled by the athlete.
So, displacement=200m

Answer 2

IF WE TAKE A CIRCLE THE DIAMETER DIVIDES THE CIRCLE INTO TWO EQUAL PARTS.THERE FOR ONE TIP OF THE DIAMETER CAN BE MARKED AS POINT A AND THE OTHER AS B.
NOW THE DIAMETER IS 200m
TIME TAKEN IS 40s
2min AND 20s CAN ALSO BE WRITTEN AS 2x60+20=140s
THEREFORE THE HE  WILL BE ABLE TO GO THREE TIMES ABOUT THE CI9RCLE i.e FROM A TO B .THEN AFTER 20  MORE SEC HE WIL BE AT POINT B ,SO THE DISPLACEMENT HERE WILL BE THE DIAMETER 200m
and the total distance travelled will be3x2 pi r+pi r =2200m distance travelled
hope u understand the pi r ,sorry it could not be written in the sign form
hope this answer helped u buddy......