A plank of mass and length is placed on a horizontal floor

PHYSICS · Single correct · CBSE · Physics · Laws of Motion · Laws of Motion

Problem

A plank of mass

2\,\text{kg}

and length

1\,\text{m}

is placed on a horizontal floor. A small block of mass

1\,\text{kg}

is placed on top of the plank at its right extreme end. The coefficient of friction between the plank and floor is

0.5

, and that between the plank and block is

0.2

. If a horizontal force of

30\,\text{N}

starts acting on the plank towards the right, the time after which the block falls off the plank is (

g=10\,\text{m s}^{-2}

): (1)

\frac{2}{3}\,\text{s}

(2)

1.5\,\text{s}

(3)

0.75\,\text{s}

(4)

\frac{4}{3}\,\text{s}