Question

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

Answer 1

Given,

mass of block $A,m=5kg$

from Newton's $2^{nd}$ law,

$F=ma$

$10=5a$

$a=2m/s^2$

Because there is no friction force between A and B. when the block A moves , block B remains at rest in its position.

Take initial velocity of $A,u=0$

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

So,$S=ut+\frac{1}{2}a{t}^2$

$0.2=0+\frac{1}{2}\times 2\times t^2$

$t^2=0.2$

$t=0.45sec$