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JEE Main & Advanced Sample Paper JEE Main Sample Paper-32

  • question_answer
    Earth's receives \[1400W/{{m}^{2}}\] of solar power. If all the solar energy falling on a lens of area \[0.2{{m}^{2}}\]is focused onto a block of ice of mass 280 g, the time taken to melt the ice will be (in min.)

    A) 10.2         

    B)                                    7.8

    C) 5.5  

    D)        4.8

    Correct Answer: C

    Solution :

    Heat received per second = (1400) (0.2) = 280 J Required heat for melting of the block\[=(0.28)(3.3\times {{10}^{5}})=9.24\times {{10}^{4}}J\]     Required time \[=\frac{9.24\times {{10}^{4}}}{280\times 60}=5.5\]min.


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