Describe how a non-zero force can act on an object over a displacement and yet do no work

I don't think it can.

- - When an object moves around a closed path, the total amount

of work that gravity does on it is zero. But so is the displacement

around the closed path.

- - When an electric charge moves around a closed path, the total

amount of work that electrostatic force does on it is zero. But so

is the displacement around the closed path.

- - If the force on the object is always perpendicular to the object's

motion during the object's displacement, then that force does no

work.

If this is the answer you had in mind, then I must say the question is

a shrewd bit of implied equivocation ... the displacement belongs to

the object, but the distance through which the force acts is zero.