WB JEE Medical WB JEE Medical Solved Paper-2014

  • question_answer
    In which of the following pairs, the two  physical quantities have different dimensions?

    A)  Plancks constant and angular momentum

    B)  Impulse and linear momentum

    C)  Moment of inertia and moment of a force

    D)  Energy and torque

    Correct Answer: C

    Solution :

       [a] Planck s constant \[=\frac{\text{Energy}}{\text{Frequency}}=\frac{[M{{L}^{2}}-{{T}^{-2}}]}{[{{T}^{-1}}]}\] Frequency   \[[M{{L}^{2}}{{T}^{-1}}]\] Angular momentum = Moment of inertia \[\times \]Angular velocity \[=[M{{L}^{2}}]\times [{{T}^{-1}}]=[M{{L}^{2}}{{T}^{-1}}]\] [b] Impulse = Force \[\times \] Time \[=[ML{{T}^{-2}}][T]=[ML{{T}^{-1}}]\] and linear momentum = Mass \[\times \] Velocity \[=[M][L{{T}^{-1}}]=[ML{{T}^{-1}}]\] [c] Moment of inertia \[\text{=}\,\text{Mass}\,\text{ }\!\!\times\!\!\text{  (Distance}{{\text{)}}^{\text{2}}}\] \[\text{ }\!\![\!\!\text{ M}{{\text{L}}^{2}}\text{ }\!\!]\!\!\text{ }\]and moment of force = Force \[\times \] Distance \[=[ML{{T}^{-2}}][L]=[M{{L}^{2}}{{T}^{-2}}]\] [d] Energy \[=[M{{L}^{2}}{{T}^{-2}}]\] and torque \[=[M{{L}^{2}}{{T}^{-2}}]\] So, [c] option has different dimensions.


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