NEET AIPMT SOLVED PAPER 2003

  • question_answer
                    The time period of a mass suspended from a spring is T. If the spring is cut into four equal parts and the same mass is suspended from one of the parts, then the new time period will be:      

    A)                 \[\frac{T}{2}\]   

    B)                 2T                          

    C)                 \[\frac{T}{4}\]                   

    D)                 T

    Correct Answer: A

    Solution :

                           Key Idea: Force constant of spring is inversely proportional to length of spring.                 Time period of mass suspended from spring.                 \[T=2\pi \sqrt{\frac{m}{k}}....(i)\]                 Now we know that,                 spring constant \[\propto \frac{1}{\text{length}}\]                 or            \[k\propto \frac{1}{x}\]                                                ...(ii)                 Since, spring is cut into four equal parts, hence force constant of each part becomes four times the previous. So,                 k' = 4k                 So, new time period of same mass suspended from one of the parts,                 \[T'=2\pi \sqrt{\frac{m}{4k}}=\frac{1}{2}.2\pi \sqrt{\frac{m}{k}}=\frac{T}{2}\]


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