JEE Main & Advanced AIEEE Solved Paper-2010

  • question_answer
      A small particle of mass m is projected at an angle\[\theta \]with the x-axis with an initial velocity \[{{v}_{0}}\] in the\[x-y\]plane as shown in the figure. At a time \[t<\frac{{{v}_{0}}\sin \theta }{g},\] the angular momentum of the particle is ?       AIEEE  Solved  Paper-2010

    A) \[\frac{1}{2}mg{{v}_{0}}{{t}^{2}}\cos \theta \hat{i}\]      

    B) \[-mg{{v}_{0}}{{t}^{2}}\cos \theta \hat{j}\]         

    C) \[mg{{v}_{0}}t\cos \theta \hat{k}\]

    D)        \[-\frac{1}{2}mg{{v}_{0}}{{t}^{2}}\cos \theta \hat{k}\]

    Correct Answer: D

    Solution :

    where\[\hat{i},\hat{j}\]and\[\hat{k}\]are unit vectors along\[x,y\] and z-axis respectively. at any time t \[\overrightarrow{r}=({{v}_{0}}cos\theta )t\hat{i}+\left( ({{v}_{0}}\sin \theta )t-\frac{1}{2}g{{t}^{2}} \right)\hat{j}\] \[\overrightarrow{v}={{v}_{0}}\cos \theta \hat{i}+({{v}_{0}}\sin \theta -gt)\hat{j}\] So, \[\overrightarrow{L}=m(\overrightarrow{r}\times \overrightarrow{v})=-\frac{1}{2}mg{{v}_{0}}{{t}^{2}}\cos \theta \hat{k}\]


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