Question

The length of simple pendulum is $1m$ and mass of its bob is $50gram$. The bob is given sufficient velocity so that the bob describes vertical circle whose radius equal to length of pendulum, the tension in the string at lowest extreme position is:

• A. $2.5N$
• B. $1N$
• C. $1.5N$
• D. $2N$

Answer 1

The correct option is A $2.5N$

Using conservation of energy,

$mg\times 2R=m{v}^2/2$

$v=2\sqrt{Rg}$ .........(1)

At lower most point, from free body digram,

$T-mg=m{v}^2/R$ ...........(2)

From (1) and (2),

$T=5mg$

$T=2.5N$