• question_answer Find frictional force on block 30 kg A)  20 N                           B)  30 N C)  40 N                           D)  50 N

As given $m=10\,kg$ FBD for upper block (10 kg) As maximum static friction $={{\mu }_{s}}N=0.5\,\times 10\times g=50N$ As 60 N is greater than force of static friction (maximum) So, block will slip over the lower one and hence force of kinetic friction ${{f}_{k}}$ has to be considered in that case. and ${{f}_{k}}={{b}_{k}}\,\,N=0.3\times 10\times 10=30\,N$             $u=\infty \,\,\Rightarrow \,\,v=f$ (from mirror formula) Also,    ${{h}_{I}}=-f\,\theta$ For plane mirror object distance is d - f. $\Rightarrow$            $x=(d-f),\,\,\,y=-f\theta$