In melde's experiment, when the tension decreases by $0.009$ kg-wt, the number of loops changes from 4 to $5…

In melde's experiment, when the tension decreases by $0.009$ kg-wt, the number of loops changes from 4 to $5 .$ The initial tension is
  1. $0.036$ kg-wt.
  2. $0 \cdot 009 \mathrm{~kg}$ -wt.
  3. $0 \cdot 018$ kg-wt.
  4. $0.025$ kg-wt.

Solution

For Melde's experiment. $\mathrm{TP}^{2}=$ constant where $\mathrm{T}$ is the tension and $\mathrm{P}$ is the number of loops. $\begin{array}{l} \therefore \mathrm{T}_{1} \mathrm{P}_{1}{ }^{2}=\mathrm{T}_{2} \mathrm{P}_{2}{ }^{2} \\ \therefore \mathrm{T}_{1}(4)^{2}=\left(\mathrm{T}_{1}-0.009\right)(5)^{2} \\ \therefore 9 \mathrm{~T}_{1}=0.009 \times 25 \\ \therefore \mathrm{T}_{1}=0.025 \mathrm{~kg}-\mathrm{wt} \end{array}$

Asked in: MHT CET 2020 (13 Oct Shift 1)

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