A particle covers half of its total distance with speed $y_1$ and the rest half distance with speed $y_2$.…

A particle covers half of its total distance with speed $y_1$ and the rest half distance with speed $y_2$. Its average speed during the complete journey is
  1. $\frac{y_1 y_2}{y_1+y_2}$
  2. $\frac{2 y_1 y_2}{y_1+y_2}$
  3. $\frac{2 y_1^2 y_2^2}{y_1^2+y_2^2}$
  4. $\frac{y_1+y_2}{2}$

Solution

Velocity $y=\frac{s}{t} \Rightarrow s=v t$ The average speed of particle $\begin{aligned} & y_{\mathrm{av}}=\frac{s+s}{\frac{s}{y_1}+\frac{s}{y_2}} \\ & y_{\mathrm{av}}=\frac{2 y_1 y_2}{y_1+y_2} \end{aligned}$

Asked in: NEET 2011 (Mains)

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