An athlete completes one round of a circular track of radius R in 40 sec. What will be his displacement at the end of 2 min. 20 sec?
Correct answer: B. 2R
- A. Zero
- B. 2R
- C. 27πR
- D. 7πR
Explanation
The athlete completes one full round of the circular track in 40 seconds. Given 140 seconds, the athlete completes 3.5 rounds (140/40 = 3.5). Completing 3 full rounds returns the athlete to the starting point, and the additional 0.5 round places him at the opposite point on the circle. The displacement in circular motion is the straight line distance from the starting point to the final point, which is the diameter of the circle: 2R.Options C and D incorrectly calculate the path traveled rather than the displacement. Option A assumes full rounds returning the athlete to the start, which isn't the case here.
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