A block of mass m is placed over a rogh surface with coefficents of static and kinetic as `mu_(s) and mu _(k) .` A force F is applied to move block .Surface f is the force of fricty=tion between block and ound . Then chose the wrong opition (s).
A. `fle mu_(s)mg "till the block not move"`
B. `f=mu_(k)` mg when the block starts moving
C. `f=F` when block Is not moving
D. `fltF` when block is moving
