The problem asks about the magnitude and direction of the normal force acting on an object with mass $m$ at rest on the floor.

Analysis:

• The object is at rest, which means it is in equilibrium, and the forces acting on it must balance out.
• The gravitational force acting downward is $F_{\text{gravity}} = mg$, where $g$ is the acceleration due to gravity.
• The normal force is the force exerted by the floor, which counters the gravitational force. To maintain equilibrium, the normal force must be equal in magnitude but opposite in direction to the gravitational force.

Thus, the normal force is:

$F_{\text{normal}} = mg \quad \text{in the upward direction}.$

Correct answer:

• Option B: $F_{\text{normal}} = mg$ in the upward direction.

Let me know if you'd like further details or explanations!

Here are five related questions to consider:

1. What is the net force acting on the object if it is at rest?
2. How would the normal force change if the object were placed on an inclined plane?
3. How does the normal force relate to the object's weight when it is not on a flat surface?
4. What would happen to the normal force if the object were accelerating upward?
5. Can you explain the difference between the normal force and gravitational force in terms of Newton's Third Law?

Tip: The normal force always acts perpendicular to the surface on which an object rests and counteracts the object's weight in situations of equilibrium on a horizontal plane.