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

Answer

A

Explanation

For just complete rotation `v=sqrt(Rg)` at top point
The rotational speed of the drum
`impliesomega=(v)/(R)=sqrt((g)/(R))=sqrt((10)/(1.25))`
The maximum rotational speed of the drum in revolutions per minute
`omega("rpm")=(60)/(2pi)sqrt((10)/(1.25))=27`