Question

To one end of a string of length $l$ a particle of mass m is attached whereas the other end is fixed A nail is located at a distance d below the point of suspension. For the ball completely swing around in a circle centred on the nail, what is the value of d in terms of length $l$?

• A. $0.4l$
• B. $0.5l$
• C. $0.6l$
• D. $0.7l$

Answer 1

Answer: (C)

$0.6l$

$\begin{array}{c}Speedrequired\\ v=\sqrt{5\times g\times \left(1-h\right)}\\ andvelocitywellballreachedbottom=\sqrt{2\times g\times l}\\ so,2\times g\times l=5\times g\left(1-h\right)\\ h=\frac{3}{5}l=0.6l\end{array}$

Hence,

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