Let F,FN AND f denote the magnitudes of the contact force,normal force and the friction exerted by one surface on the other in contact.If none of these is zero,A)F>FN B)F>f C)FN>f D)FN-f<F<FN+f.Contact force has to be smaller than frictional and normal force .My dobt is in option d.
As we know that contact force is resultant of normal and
frictional force and angle between normal and frictional
force is 90 degree,therfore,option A and B are correct.
Also, fricctional f=u.F(N) and value of u can be greater
or smaller than 1,therefore,option C is incorrect.
Now,F(N)-f and F(N)+f are the min and max values
of resultant of both forces and we kow that contact force
is resultant of these two and angle f and F(N) is fixed
i.e. 90 degree.therfore option D is also correct..
Okay understood.Thanks.