Multiple choice

A body covers one third of the distance with speed ${V_1}$ and two third of the distance with speed ${V_2}$. The average speed of the body is:

  1. $\frac{{{V_1} + {V_2}}}{2v_2}$
  2. $\frac{{{V_1} + {V_2}}}{2}$
  3. $\frac{{3{V_1}{V_2}}}{{2{V_1} + {V_2}}}$
  4. $\frac{{3{V_1}{V_2}}}{{{V_1} + 2{V_2}}}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Average speed = Total distance / Total time. Let total distance be D. Time = (D/3)/V1 + (2D/3)/V2 = D(V2 + 2V1) / (3V1V2). Average speed = D / (D(V2 + 2V1) / 3V1V2) = 3V1V2 / (2V1 + V2).

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