Cement, sand and seree are dropped in rotating cylidrical drum to make concrete mixture. If rotating speed of drum is very high then contents are attached to wall of drum and mixture is not formed correctly. If radius of drum is 1.25 m and its axis is horizontal, then the required maximum rotating speed to make good mixture in rpm is -

Options

A. `0.4`
B. `1.3`
C. `8.0`
D. `27.0`

Answer

D

Explanation

Given, `r=1.25,g=9.81m//s^(2)`, centrifugal force is greater than weight for maximum speed of roation of cement and concrete.
`omega^(2)rgtgimpliesomega=sqrt((g)/(r))=2.8` rad/s
`2pi` radian has 1 revolution.
1 radian/s `(1)/(2pi)` revolution
2. 8 radian/s `(2.8)/(2pi)` rev/s
To get in rpm
`omega=(2.8)/(2pi)xx60=26.73"rpm"~~27`