Manipal Engineering Manipal Engineering Solved Paper-2013

  • question_answer
    The speed of a wave on a string is\[150\text{ }m/s\]when the tension is\[120N\]. The percentage increase in the tension in order to raise the wave speed by\[20%\] is

    A) \[44%\]                               

    B) \[40%\]

    C) \[20%\]               

    D)        \[10%\]

    Correct Answer: A

    Solution :

    We know that\[v=\sqrt{\frac{T}{m}}\]                 \[v\propto \sqrt{T}\]                 \[\frac{{{v}_{1}}}{{{v}_{2}}}\,=\sqrt{\frac{{{T}_{1}}}{{{T}_{2}}}}\]                 \[\frac{{{v}_{1}}}{{{v}_{2}}}={{\left( \frac{{{v}_{1}}}{{{v}_{2}}} \right)}^{2}}\]                 \[\frac{{{T}_{2}}-{{T}_{1}}}{{{T}_{1}}}=\frac{v_{1}^{2}-v_{1}^{2}}{v_{1}^{2}}\]                 \[{{v}_{2}}={{v}_{1}}+\frac{20}{100}{{v}_{1}}=\frac{120}{100}{{v}_{1}}=\frac{6}{5}{{v}_{1}}\]                 \[=\frac{6}{5}\times 150\]                 \[\frac{{{T}_{2}}-{{T}_{1}}}{{{T}_{1}}}=\frac{{{(180)}^{2}}-{{(150)}^{2}}}{{{(150)}^{2}}}\]                 \[=\frac{30\times 330}{150\times 180}=0.47\]                 \[=\frac{{{T}_{2}}-{{T}_{1}}}{{{T}_{1}}}\times 100=0.44\times 100=44%\]


You need to login to perform this action.
You will be redirected in 3 sec spinner