Question

a 2kg object is moving horizontally with a speed of 4 m/s.how much net force is required to keep the object moving at this speed and in this direction?

Answer 1

If the object is moving in a straight line with constant speed,
that's a description of " acceleration = zero ".

Zero acceleration means zero net force on the object.

NO net force is 'required' to keep an object moving in a straight line
at constant speed.  In fact, if there IS any net force on the object,
then either its speed or its direction MUST change ... there's no way
to avoid it.

None of this depends on the object's mass, or on the speed or direction
of its motion.