Final answer:
The weight of the anvil and the normal force from the surface are the two balanced forces acting on the anvil in Bill’s demonstration, keeping it in static equilibrium.
Step-by-step explanation:
The two balanced forces that act upon the anvil in Bill’s demonstration are likely the weight of the anvil and the normal force from the surface on which the anvil rests.
These two forces are equal in magnitude but opposite in direction, resulting in no net force on the anvil, which keeps it in static equilibrium.
As long as there are no other horizontal forces acting on the anvil, the system remains at rest or moves with constant velocity, according to Newton's first law of motion.