CET Karnataka Medical CET - Karnataka Medical Solved Paper-2012

  • question_answer
    A body of mass m is travelling with a velocity u. When a constant retarding force F is applied, it comes to rest after travelling a distance \[{{s}_{1}}\]. If the initial velocity is 2u, with the same force F, the distance travelled before it comes to rest is \[{{s}_{2}}\]. Then

    A)  \[{{s}_{2}}=2{{s}_{1}}\]           

    B)  \[{{s}_{2}}=\frac{{{s}_{1}}}{2}\]

    C)  \[{{s}_{2}}={{s}_{1}}\]             

    D)  \[{{s}_{2}}=4{{s}_{1}}\]

    Correct Answer: D

    Solution :

    : By applying constant retarding force F the  body is brought to rest so \[\upsilon =0\].              Retardation, \[a=-\frac{F}{m}\] If s be distance travelled by the body before it  comes to rest (called stopping distance). Using 3rd equation of motion         \[{{\upsilon }^{2}}-{{\upsilon }^{2}}=2as\] \[{{(0)}^{2}}-{{u}^{2}}=2\left( -\frac{F}{m}s \right)\] \[s=\frac{{{u}^{2}}m}{2F}\]              \[s\propto {{u}^{2}}\]For the same of m.F. \[\therefore \] \[\frac{{{s}_{1}}}{{{s}_{2}}}={{\left( \frac{u}{2u} \right)}^{2}}=\frac{1}{4}\] or \[{{s}_{2}}=4{{s}_{1}}\]


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