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NEET Sample Paper NEET Sample Test Paper-80

  • question_answer
    A metal disc of radius r floats on the surface of water. The water layer goes down and makes an angle 9 with the vertical edge of the disc. If it displaces a weight w of water and the surface tension of water is T, then weight of disc is

    A)  \[2\pi r\,T\,cos\,\theta \]             

    B)  \[2\pi rT\]

    C)  \[2\pi r\,T\,cos\,\theta +w\]        

    D)  \[2\pi r\,T\,cos\,\theta -w\]

    Correct Answer: C

    Solution :

    When water is depressed downwards at point of contact, then the force due to surface tension acts upwards. Therefore, apparent weight \[=\,\,\,{{F}_{T}}\,\,+ w = 2\pi  r T\,cos \theta  +\,\,w\]


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