Please answer the 3 question

Dear Student, Friction force F=μN N is normal reaction 1) N is directly proportional to weight of the body and it also depend on the inclination of the plane with horizontal.so friction force is also directly proportional to weight of the body. 2) If the surfaces in contact are smooth then friction is less and if the surface are rough then the friction force is more. 3) The force due to friction is generally independent of the contact area between the two surfaces but when the surface area gets too small then the coefficient of friction increases because the object may begin to dig into the surface which increases frictional force. Regards