Gujarati
2.Motion in Straight Line
medium

If the body covers one-third distance at speed $v_1$, next one third at speed $v_2$ and last one third at speed $v_3$, then average speed will be

A

$\frac{{{\upsilon _1}\,{\upsilon _2} + {\upsilon _2}\,{\upsilon _3} + {\upsilon _3}\,{\upsilon _1}}}{{{\upsilon _1} + {\upsilon _2} + {\upsilon _3}}}$

B

$\frac{{{\upsilon _1} + {\upsilon _2} + {\upsilon _3}}}{3}$

C

$\frac{{{\upsilon _1}\,{\upsilon _2}\,{\upsilon _3}}}{{{\upsilon _1}\,{\upsilon _2} + {\upsilon _2}\,{\upsilon _3} + {\upsilon _3}\,{\upsilon _1}}}$

D

$\frac{{3{\upsilon _1}\,{\upsilon _2}\,{\upsilon _3}}}{{{\upsilon _1}\,{\upsilon _2} + {\upsilon _2}\,{\upsilon _3} + {\upsilon _3}\,{\upsilon _1}}}$

Solution

(d) ${v_{av}} = \frac{x}{{\frac{{x/3}}{{{v_1}}} + \frac{{x/3}}{{{v_2}}} + \frac{{x/3}}{{{v_3}}}}} = \frac{{3{v_1}{v_2}{v_3}}}{{{v_1}{v_2} + {v_2}{v_3} + {v_1}{v_3}}}$

Standard 11
Physics

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