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CBSE Class 9 Answered

An athlete complete one round of a circular track of diameter 40 m in 12 sec. What will be the distance covered and displacement at the end of 42 sec
Asked by Satakshi Srivastava | 12 May, 2013, 08:50: PM
answered-by-expert Expert Answer
The person takes 12 seconds to complete 1 round.
42 = 12 + 12 + 12 + 6
So at the end of 42 seconds he will have completed 3 full and 1 half circle.
So he will be at the point diametrically opposite to the point from where he started at t = 0.
 
So, displacement = 2R = D = 40m
 
Now, R=20m
Distance = 3 Full circles + 1 half circle
= 3x2x?xR + ?xR = 7x?xR = 22x20 = 440m is the distance.
 
Answered by | 12 May, 2013, 09:02: PM

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