if an object is pushed along a rough horizontal surface and moves at a constant velocity, then...

Answer 1

it does not accelerate.

the friction exactly balances the motive force.

Answer 2

F-Fk = M*a.
F-Fk = M*0,
F-Fk = 0,
F = Fk. = Force of kinetic energy.

Answer 3

Correction: F = Fk = Force of kinetic friction.