JEE Main 2016 Physics question
Concrete mixture is made by mixing cement, stone and sand in a rotating cylindrical drum. If the drum rotates too fast, the ingredients remain stuck to the wall of the drum and proper mixing of ingredients does not take place. The maximum rotational speed of the drum in revolutions per minute (rpm) to ensure proper mixing is close to : (Take the radius of the drum to be m and its axle to be horizontal) :
Solution
The critical condition occurs at the **top** of the drum, where gravity and the normal force both point towards the centre. The ingredients just stay in contact when the normal force falls to zero and gravity alone supplies the centripetal force:
mg = mω^2R ⇒ ω = =
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