sphere is already rotaing with some  so the sphere will have a tendency to move in the rightward direcrtion so friction will act leftwards.

 

f = k(mg)

 

a torque is produced by friction, it causes an angular retadation   

 

 = /I

   

   = 5kg/2R

 

so,

 

0 =  - (5kg/2R)t

 

so,

 

t = (2R)/5Kg     

 

the other smooth surface that the sphere is in contact with will only disable the sphere from moving leftwards.

 

i dont know if this is correct., waiting for conformation from Karthik2007:)