QJEEM16Pha3ea: JEE Main 2016 Physics - Class 11 JEEM16Pha3ea Solution: Concrete mixture is made by mixing cement, stone and sand in a…

For proper mixing, the concrete mixture should not stick to the top wall of the cylinder and it should fall down.

The maximum velocity at the top is v, then we have

${{m{v^2}} \over r} = mg$

$\Rightarrow v = \sqrt {rg}$

Therefore, the maximum rotational speed of the drum is

$\omega = {v \over r} = \sqrt {{g \over r}} = \sqrt {{{9.8} \over {1.25}}}$ rad/s

$= \sqrt {{{9.8} \over {1.25}}} \times {{60} \over {2\pi }}$ rpm = 26.74 $\approx$ 27 rpm