Manipal Engineering Manipal Engineering Solved Paper-2009

  • question_answer
     Ana-particle of mass \[6.4\times {{10}^{27}}\]kg and charge \[3.2\times {{10}^{-19}}\] C is situated in a uniform electric field of \[1.6\times {{10}^{5}}\,V{{m}^{-1}}\] The velocity of the particle at the end of \[2\times {{10}^{-2}}\] m path when it starts from rest is

    A)  \[3\sqrt{3}\times {{10}^{5}}m{{s}^{-1}}\]            

    B) \[5\times {{10}^{5}}m{{s}^{-1}}\]

    C)  \[16\times {{10}^{5}}m{{s}^{-1}}\]    

    D)        \[4\sqrt{2}\times {{10}^{5}}m{{s}^{-1}}\]

    Correct Answer: D

    Solution :

    Given,\[{{m}_{\alpha }}=6.4\times {{10}^{-27}}kg\]                 \[{{q}_{\alpha }}=3.2\times {{10}^{-19}}C,\,\,E=1.6\times {{10}^{5}}\,\,V{{m}^{-1}}\] Force on\[\alpha -\]particle                 \[F={{q}_{\alpha }}E=3.2\times {{10}^{-19}}\times 1.6\times {{10}^{5}}\]                     \[=51.2\times {{10}^{-15}}N\] Now, acceleration of the particle                 \[\alpha =\frac{F}{{{m}_{\alpha }}}=\frac{51.2\times {{10}^{-15}}}{6.4\times {{10}^{-27}}}\]                    \[=0.8\times {{10}^{13}}\,\,m{{s}^{-2}}\] \[\because \]Initial velocity,\[u=0\] \[\therefore \]  \[{{v}^{2}}=2\alpha S\]                      \[=2\times 8\times {{10}^{12}}\times 2\times {{10}^{-12}}\]                      \[=32\times {{10}^{10}}\] or            \[v=4\sqrt{2}\times {{10}^{5}}\,\,m{{s}^{-1}}\]


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