RAJASTHAN PMT Rajasthan - PMT Solved Paper-2010

  • question_answer
    If the work done in blowing a bubble of volume V is W then the work done in blowing bubble of volume 2 V from the same soap solution will be

    A)  W/2                                     

    B)  \[\sqrt{\text{2}}\,\text{W}\]

    C)  \[\sqrt[\text{3}]{\text{2}}\,\text{W}\]                 

    D)         \[\sqrt[\text{3}]{\text{4}}\,\text{W}\]

    Correct Answer: B

    Solution :

    Work done to form a soap bubble                 \[W=8\pi {{R}^{2}}T\]                 \[[\because \,\,V\propto {{R}^{2}}\Rightarrow R\propto {{V}^{2/3}}]\] or            \[\frac{{{W}_{2}}}{{{W}_{1}}}={{\left( \frac{{{V}_{2}}}{{{V}_{1}}} \right)}^{2/3}}={{(2)}^{2/3}}\] or            \[{{W}_{2}}={{(4)}^{1/3}}{{W}_{1}}={{(4)}^{1/3}}W\]


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