Question

A cone filled with water is revolved in a vertical circle of radius $4m$ and the water does not fall down. What must be the maximum period of revolution?

• A. $2s$
• B. $4s$
• C. $1s$
• D. $6s$

Answer 1

The correct option is B $4s$

Applying Bernouilli theorem,
When a cone filled with water is revolved in a vertical circle, then the velocity at the higher point given by
$v\le \sqrt{gr}$
$v=r\omega =r\frac{2\pi }{T}$
$\frac{2\pi r}{T}\le \sqrt{rg}$
$T\ge \frac{2\pi r}{\sqrt{rg}}=2\pi \sqrt{\frac{r}{g}}=2\pi \sqrt{\frac{4}{9.8}}$
$=2\times 3.14\times 0.6389=4.0s$
$T_{max}=4s$