A plank of mass \( 2 \mathrm{~kg} \) and length \( 1 \mathrm{~m} \) is placed on a horizontal fl...

A plank of mass \( 2 \mathrm{~kg} \) and length \( 1 \mathrm{~m} \) is placed on a horizontal floor. A small block of mass
\( \mathrm{P} \) \( 1 \mathrm{~kg} \) is placed on top of the plank, at its right

W extreme end. The coefficient of friction between plank and floor is \( 0.5 \) and that between plank and block is 0.2. If a horizontal force \( =30 \mathrm{~N} \) starts acting on the plank to the right, the time after which the block will fall off the plank is
(1) \( (2 / 3) s \)
(2) \( 1.5 \mathrm{~s} \)
(3) \( 0.75 \mathrm{~s} \)