Use Relative Velocity to find time and number of laps

  • M0★ M1

    Given: There are 2 people in race.
    Trainer finishes 1 lap in 75 seconds.
    Olympic runner finishes 1 lap in 57 seconds.

    Suppose race track length = 1425m.

    I selected 1425 because 1425 is lcm of 57 and 75.

    Speeds:
    1) Trainer = 19 m/s
    2) Olympic runner = 25m/s

    Relative speeds:
    1) Trainer = 0 m/s (Trainer is stationary)
    2) Olympic runner = 6 m/s

    Distance/Speed = Time
    Assume Trainer is at the start of the lap and is stationary.

    Time taken by Olympic runner to complete the lap and to catch trainer who is standing at the start of the lap = Time to catch up.

    Time to catch up : 1425m/6m/s = 237.5 seconds

    It means, say race starts time T = 0 then, when T = 237.5 s. The overlap will happen.

    So Trainer need 75 seconds for 1 lap. Then how many laps in 237.5 seconds.
    Number of Trainer laps = 237.5/75 = 3.17(Approximately)

  • M0★ M1

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