Question
The bob of a simple pendulum of length 1m has mass 100g and a speed of 1.4m/s at the lowest point in its path. Find the tension in the string at this instant.
✓
Answer
At the lowest pt.$\text{T}=\text{mg}+\frac{\text{mv}^2}{\text{r}}$
Here $\text{m}=100\text{g}=\frac{1}{10}\text{kg},\ \text{r}=1\text{m},\ \text{v}=1.4\text{m}/\text{sec}$
$\text{T}=\text{mg}+\frac{\text{mv}^2}{\text{r}}$
$\Rightarrow\frac{1}{10}\times9.8\times\frac{(1.4)^2}{10}$
$=0.98+0.196=1.176=1.2\text{N}$
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