NEET Physics Motion in a Straight Line / सरल रेखा में गति NEET PYQ-One Dimensional Motion

  • question_answer
    The distance travelled by a particle starting from rest and moving with an acceleration \[\frac{4}{3}m{{s}^{-2}},\] in the third second is               [AIPMPT (S) 2008]

    A) 6 m

    B) 4 m                  

    C) \[\frac{10}{3}m\]

    D) \[\frac{19}{3}m\]

    Correct Answer: C

    Solution :

    Distance travelled by the particle in nth second is\[{{S}_{nth}}=u+\frac{1}{2}a(2n-1)\] where u is initial speed and a is acceleration of the particle.
    Here,     \[n=3,u=0,a=\frac{4}{3}m/{{s}^{2}}\]
    \[\therefore \]      \[{{S}_{3rd}}=0+\frac{1}{2}\times \frac{4}{3}\times (2\times 3-1)\]
    \[=\frac{4}{6}\times 5\]
    \[=\frac{10}{3}m\]
    Alternative: Distance travelled in the 3rd Second = distance travelled in 3s distance travelled in 2s
    As,        \[u=0,\]
                \[\,{{S}_{(3rd\,s)}}=\frac{1}{2}a{{.3}^{2}}-\frac{1}{2}a{{.2}^{2}}=\frac{1}{2}.a.5\]
    Given    \[a=\frac{4}{3}m{{s}^{-2}}\]
    \[\therefore \]      \[{{D}_{(3rd\,s)}}=\frac{1}{2}\times \frac{4}{3}\,\times 5=\frac{10}{3}\,m\]


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