The block weighs 20 Newtons, which means that the force due to gravity acting on it is 20 N downward. Since the block is resting on a flat surface and there are no vertical accelerations, the normal force exerted by the table on the block will be equal in magnitude to the gravitational force to balance it.

Thus, the magnitude of the normal force is 20 Newtons.

Would you like more details or have any further questions?

Here are 5 related questions:

1. How would the normal force change if the table were inclined at an angle?
2. What is the normal force if the block were accelerating upwards?
3. How is the normal force related to friction?
4. What would happen to the normal force if the block were lifted slightly above the table?
5. If the block were submerged in water, how would that affect the normal force?

Tip: The normal force always acts perpendicular to the surface and balances forces in the vertical direction when there's no vertical acceleration.