NEET AIPMT SOLVED PAPER SCREENING 2010

  • question_answer
    A tuning fork of frequency 512 Hz makes 4 beats/s with the vibrating string of a piano. The beat frequency decreases to 2 beats/s when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was                

    A) 510 Hz   

    B)                        514-Hz               

    C) 516 Hz                  

    D)        508 Hz                

    Correct Answer: D

    Solution :

    Suppose \[{{n}_{p}}=\] frequency of piano =? \[({{n}_{p}}\propto \sqrt{T})\]\[{{n}_{f}}=\]frequency of tuning fork = 512 Hz x = Beat frequency = 4 beats/s, which is decreasing \[(4\to 2)\] after changing the tension of piano wire. Also, tension of piano wire is increasing so \[{{n}_{p}}\uparrow \] Hence, \[{{n}_{p}}\uparrow -{{n}_{f}}=x\downarrow \xrightarrow[{}]{{}}\text{worng}\] \[{{n}_{p}}-{{n}_{p}}\uparrow =x\downarrow \xrightarrow[{}]{{}}\text{correct}\] \[\Rightarrow {{n}_{p}}={{n}_{f}}-x=512-4=508\,Hz\]


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