Using a horizontal force $F$, a table is moved across the floor at a constant velocity. How much is the frictional force exerted by the floor on the table?

Since the table moves with constant velocity, its acceleration is zero. Therefore, the net force acting on the table is zero.

The two horizontal forces acting on the table are:

Applied force = F (forward)

Frictional force = f (backward)

For the net force to be zero:

$$f = F$$

Therefore, the frictional force exerted by the floor on the table is equal in magnitude to F, but it acts in the direction opposite to the motion.