Question

The bob of a simple pendulum of length $1m$ has mass $100g$ and a speed of $1.4m/s$. Find the tension in the string at this instant.

• A. $13N$
• B. $1.196N$
• C. $15N$
• D. None of these

Answer 1

The correct option is B $1.196N$

At lowest point ,two force are acting on the bob

(a)Tension in string upward.

(b)mg downward

As it is moving along circular path

Hence,

$\begin{array}{c}T-mg=m{v}^{2}rT-m{v}^{2}r\\ \Rightarrow T=mg+m{v}^{2}rT=mg+m{v}^{2}r\\ Given,\\ mm=100g=0.1kg\\ v=1.4m/s\\ r=1m\\ g=10m{s}^{-2}\\ Hence,\\ T=1.196N\end{array}$

Hence,

option $B$ is correct answer.