A block of mass 10 Kg  is in contact against the inner wall of a hollow cylinder drum of radius 1 m . The coefficient of friction  between the block and the iner wall of the cylinder is 0.1 . The minimum angular velocity needed for the cylinder  to keep the block  stationary when the cylinder is vertical and rotating about its axis will be  Option 1) $\sqrt {10} rad /s$ Option 2) $(10 / 2 \pi) rad / s$ Option 3) $10 rad /s$ Option 4) $10 \pi rad /s$

$mg = \mu N \\\\ N = m \omega ^ 2 R \\\\ mg = \mu m \omega ^ 2 R \\\\ \omega ^ 2 = 10 /0.1 \\\\ \omega = 10$

Option 1)

$\sqrt {10} rad /s$

Option 2)

$(10 / 2 \pi) rad / s$

Option 3)

$10 rad /s$

Option 4)

$10 \pi rad /s$

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