Question

A small block $B$ is placed in another block $A$ of mass $5kg$ and length $20cm$. Initially the block $B$ is near the right end of block $A$. A constant horizontal force of $10N$ is applied to the block $A$. All the surface are assumed friction-less. Find the time elapsed before the block $B$ separates from $A$.

Answer 1

$m=5kg$ of block $A$

$ma=10N$

$\Rightarrow a=10/5=2m/s^2$

As there is no friction between $A$ & $B$, when the block $A$ moves, Block $B$ remains at rest in its position.Initial velocity of $A=u=0$.

Distance to cover so that $B$ separate out $s=0.2m$

Acceleration $a=2m/s^2$

$\therefore s=ut+1/2a{t}^2$

$\Rightarrow 0.2=0+\left(1/2\right)\times 2\times t^2$

$\Rightarrow t^2=0.2\Rightarrow t=0.44sec\Rightarrow t=0.45sec$.