JEE Main & Advanced Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति JEE PYQ - Work Energy Power and Collision

  • question_answer
    The average mass of rain drops is \[3.0\times {{10}^{-5}}\]kg and their avarage terminal velocity is 9 m/s. Calculate the energy transferred by rain to each square metre of the surface at a place which receives 100 cm of rain in a year.          [JEE ONLINE 11-04-2014]

    A) \[3.0\times {{10}^{5}}J\]

    B) \[4.05\times {{10}^{4}}J\]

    C) \[3.0\times {{10}^{5}}J\]

    D) \[9.0\times {{10}^{4}}J\]

    Correct Answer: B

    Solution :

    [b] Total volume of rain drops, received 100 cm in a year by area \[1{{m}^{2}}\]\[1{{m}^{2}}\times \frac{100}{100}m=1{{m}^{3}}\]
    As we know, density of water,\[d={{10}^{3}}kg/{{m}^{3}}\]
    Therefore, mass of this volume of water
    \[M=d\times v={{10}^{3}}\times 1={{10}^{3}}kg\]
    Average terminal velocity of rain drop v = 9 m/s (given)
    Therefore, energy transferred by rain,
    \[E=\frac{1}{2}m{{v}^{2}}\]               \[=\frac{1}{2}\times {{10}^{3}}\times {{(9)}^{2}}\]
    \[=\frac{1}{2}\times {{10}^{3}}\times 81=4.05\times {{10}^{4}}J\]


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