$\overrightarrow{ v }=0.5 t ^{2} \hat{ i }+3 t \hat{ j }+9 \hat{ k }$
$\overrightarrow{ v }_{ at\,t =2}=2 \hat{ i }+6 \hat{ j }+9 \hat{ k }$
$\therefore$ Angle made by direction of motion of mosquito will be,
$\cos ^{-1} \frac{2}{11}($ from $x$ -axis $)=\tan ^{-1} \frac{\sqrt{117}}{2}$
$\cos ^{-1} \frac{6}{11}($ from $y$ -axis $)=\tan ^{-1} \frac{\sqrt{85}}{6}$
$\cos ^{-1} \frac{9}{11}($ from $z$ -axis $)=\tan ^{-1} \frac{\sqrt{40}}{9}$
None of the option is matching.
Hence this question should be bonus.
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Assertion $A$ : When a rod lying freely is heated, no thermal stress is developed in it.
Reason $R :$ On heating the length of the rod increases.
In the light of the above statements, choose the correct answer from the options given below
