A runner covers the first half of a course at v1 = 4.0\text{ m/s} and the second half at v2 = 6.0\text{ m/s}. What is the average speed over the whole course?

4.8 m/s For equal distances, the harmonic mean applies: \bar v = 2v1 v2/(v1+v2) = 2(4)(6)/10 = 48/10 = 4.8\text{ m/s}.

Displacement, Velocity, and Acceleration

AP Physics 1· difficulty 4/5

v_1 = 4.0\text{ m/s}

Explanation

\bar v = 2v_1 v_2/(v_1+v_2) = 2(4)(6)/10 = 48/10 = 4.8\text{ m/s}

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