KinematicsMedium
Question
Two athletes, A and B, run in the ground on an oval track of length L (say) at 8.0 m/s and 6.0 m/s respectively in the same direction starting from same initial point. How many laps (rounds) will the athlete. A complete on the track before overtaking athletes B for the first time.
Options
A.2
B.3
C.4
D.5
Solution
Sol. Key concept: Overtaking on a closed track requires one full lap of relative gain.
The relative speed of A with respect to B is 8 − 6 = 2 m s⁻¹. At the first overtaking, A has gained one complete track length L.
$$t = \frac{L}{8 - 6} = \frac{L}{2},\ \ \ \ \ s_{A} = 8t = 4L$$
Thus, A completes four laps by the first overtaking, while B completes three. Hence (c).
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