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InterviewSolution
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An athelete complete one round of a circular track of diameter of 200m in 40s. What will be the displacement of the end of 2minutes 40 seconds? |
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Answer» One round completed by athlete in 40 sec. In 2 min 40 sec or 160 seconds athlete complete = 160/40= 4 rounds. As athlete start the race and end it at same point. So displacement is zero We know that, velocity along a circular path =Circumferencetime=Circumferencetime⇒v=2πr40s⇒v=2πr40s⇒v=2×3.14×100m40s⇒v=2×3.14×100m40s⇒v=628m40s⇒v=628m40s⇒v=15.7m/s⇒v=15.7m/s(a) Distance after 140sWe know that,distance=velocity ×time⇒ distance=15.7m/s ×140 s = 2198 m(b) Displacement after 2 m 20 s i.e. in 140 sSince,rotatin in 40 s=1Therefore, rotation in 1s=1401s=140∴ rotation in 140s=140×140=3.5140s=140×140=3.5Therefore, in 3.5 rotations athlete will be just at the opposite side of the circular track, i.e. at a distance equal to the diameter of the circular track which is equal to 200 m.Therefore, Distance covered in 2 m 20 s = 2198 mAnd, displacement after 2 m 20 s = 200m |
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