MCQ
A simple pendulum has time period $T$. The bob is given charge and surface below it is given positive charge. The new time period will be:
- ✓Less than $T$
- BGreater than $T$
- CEqual to $T$
- DInfinite
✓
Answer
Correct option: A.
Less than $T$
$\text{g}'=\text{g}+\frac{\text{F}_{\text{e}}}{\text{m}},\text{g}'>\text{g}$
Since, $\text{T}=\sqrt{\frac{\text{l}}{\text{g}}}$
So $\text{T}\propto\frac{1}{\sqrt{\text{g}}}$ and $\text{T}'\propto\frac{1}{\sqrt{\text{g}'}}$
$\therefore\text{T}'<\text{T}$
Since, $\text{T}=\sqrt{\frac{\text{l}}{\text{g}}}$
So $\text{T}\propto\frac{1}{\sqrt{\text{g}}}$ and $\text{T}'\propto\frac{1}{\sqrt{\text{g}'}}$
$\therefore\text{T}'<\text{T}$
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