JEE Main & Advanced Physics Motion in a Straight Line / सरल रेखा में गति Question Bank Self Evaluation Test - Motion in a Strainght Line

  • question_answer
    A particle is moving along a straight line path according to the relation \[{{s}^{2}}=a{{t}^{2}}+2bt+c\]   s represents the distance travelled in t seconds and a, b, c are constants. Then the acceleration of the particle varies as

    A) \[{{s}^{-\,3}}\]       

    B) \[{{s}^{3/2}}\]

    C) \[{{s}^{-2/3}}\]  

    D) \[{{s}^{2}}\]

    Correct Answer: A

    Solution :

    \[{{s}^{2}}=a{{t}^{2}}+2bt+c\text{       }\therefore \text{  2s}\frac{ds}{dt}=2at+2b\] \[\text{or }\frac{ds}{dt}=\frac{at+b}{s},\text{ again differrentiating}\] \[\frac{{{d}^{2}}s}{d{{t}^{2}}}=\frac{a{{s}^{2}}-{{\left( at+b \right)}^{2}}}{{{s}^{3}}}\text{    }\therefore \text{a=}\frac{{{d}^{2}}s}{d{{t}^{2}}}\propto {{s}^{-3}}.\]


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