Question

A particle moves on a circular path of radius 'r' , It completes one revolution in 40 s . Calculate the distance in 2 min 20 sec. ?
Ans is 2r

Answer 1

no of revolutions completed in 40 s = 1
no of revolutions completed in 1s = 1/40

no of revolutions completed in 2 min 20 sec or 140 s = 1/40×140 => 7/2 or 3.5 revolutions

radius = r
circumference = 2πr
total distance travelled in 2 min 20 sec.

=> 3.5×2πr

#recheck your answer .

Answer 2

Time in seconds=2×60+20=140sec
Circumference=2πr
No. Of rounds completed by it in 140sec = 140/40 =3.5
Therefore total distance covered covered by him = no. of rounds×circumference =3.5×2πr
=7πr


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