A solid sphere of mass 3 kg is kept on a horizontal surface. The coefficient of static friction between the surfaces in contact is 2/7. What maximum force can be applied at the highest point in the horizontal direction so that the sphere does not slip on the surface? (in N)

F+f=ma   ……….(i)Torque equation about the centre of mass of the sphere    F r-f r = Icom×α   (Assuming force of friction acts in the forward direction at the point of contact with the surface )⇒F-f = 1r25mr2×α ⇒F-f = 25mrα..........ii Also  a = rα ......iii Solving f = 37F The sphere will not slip if f≤μmg                                           ⇒37F≤μmg                                            ⇒F≤73×27×3×10 N                                             ⇒F≤20 N