Question

A sphere of radius $25$ cm and mass $1$ kg is hung by a string of negligible mass and length $40cm$, then tension in the string is (take $g=10m{s}^{-2}$ )

• A. $12.8N$
• B. $18.4N$
• C. $10N$
• D. $8N$

Answer 1

The correct option is A $12.8N$

angle made with horizontal

$\theta ={\cos }^{-1}\left(\frac{25}{40}\right)=51.317$

from force balance$,$

vertical component of tension $=mg$

$\begin{array}{c}T\sin \theta =mg\\ T\sin 51.37=1\left(10\right)\\ T=\frac{10}{0.78119}=12.8N\end{array}$

Hence,

option $\left(A\right)$ is correct answer.