JEE Main & Advanced Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति Question Bank Mock Test - Work Power and Energy

  • question_answer
    A spring is compressed between two toy carts of masses \[{{m}_{1}}\]and\[{{m}_{2}}\]. When the toy carts are released, the spring exerts on each toy cart equal and opposite forces for the same small time \[t\]. If the coefficients of friction \[\mu \] between the ground and the toy carts are equal, then the magnitude of displacements of the toy carts are in the ratio

    A) \[\frac{{{S}_{1}}}{{{S}_{2}}}=\frac{{{m}_{2}}}{{{m}_{2}}}\]       

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

    C) \[\frac{{{S}_{1}}}{{{S}_{2}}}={{\left( \frac{{{m}_{2}}}{{{m}_{1}}} \right)}^{2}}\]

    D) \[\frac{{{S}_{1}}}{{{S}_{2}}}={{\left( \frac{{{m}_{1}}}{{{m}_{2}}} \right)}^{2}}\]

    Correct Answer: C

    Solution :

    [c] Minimum stopping distance =s Work done against the friction \[=W=\mu mgs\] Initial momentum gained by both toy carts will be same because same force acts for same time initial kinetic energy of the toy cart =\[\left( \frac{{{p}^{2}}}{2m} \right)\] Therefore, \[\mu mgs=\frac{{{p}^{2}}}{2m}\]or \[s=\left( \frac{{{p}^{2}}}{2\mu g{{m}^{2}}} \right)\] For the two toy carts, momentum is numerically the same. Further \[\mu \]and g are the same for the toy carts. So, \[\frac{{{S}_{1}}}{{{S}_{2}}}={{\left( \frac{{{m}_{2}}}{{{m}_{1}}} \right)}^{2}}\]       


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