Left finger will keep slipping till the kinetic friction is less than the static friction on right finger. After that right finger will start slipping. It will slip till the kinetic friction on it is less than static friction on the left one. NLx=NR×0.4 NL+NR=Mg ⇒NL=
Mg×0.4
x+0.4
and NR=
Mgx
x+0.4
µkNL≥µsNR
0.32×Mg×0.4
x+0.4
≥
0.4×Mgx
x+0.4
x=
0.4×0.32
0.4
=0.32m Now right finger will start moving and it will stop, when kinetic friction on it will be more than static friction on left finger. NL×0.32=NRXR NL+NR=Mg and µkNR≥µgNL 0.32×