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2. motion in straight line — Physics STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 SciencePhysics2. motion in straight line1 Mark
MCQ
A car covers $A B$ distance with first one-third at velocity $v _{1} ms ^{-1}$, second one-third at $v _{2} ms ^{-1}$ and last one-third at $v _{3} ms ^{-1}$. If $v _{3}=3 v _{1}, v _{2}=2 v _{1}$ and $v _{1}=11\,ms ^{-1}$ then the average velocity of the car is________ $ms ^{-1} .$
  • A
    $17$
  • B
    $16$
  • C
    $20$
  • ✓
    $18$
✓

Answer

Correct option: D.
$18$
d
$\langle\overrightarrow{ v }\rangle=\frac{\text { Displacement }}{\text { time }}$

(Let displacement be $l$ )

$=\frac{\ell}{\left(\frac{\ell}{ V _{3}}+\frac{\ell}{ V _{2}}+\frac{\ell}{ V _{1}}\right) \frac{1}{3}}$

$=\frac{3}{\frac{1}{ V _{1}}+\frac{1}{ V _{2}}+\frac{1}{ V _{3}}}=\frac{3}{\frac{1}{11}+\frac{1}{22}+\frac{1}{33}}$

$=18\,m / s$

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