Aman drags a 12.0 kg bag of mulch at a constant speed applying a 39.5 n force at 41°. what is the normal force acting on the bag?

The normal force is perpendicular to the surface. Its intensity is equal to the force pressing the object against the surface, but it has opposite direction.
We need to calculate the force pushing the bag down in order to calculate normal force.
The force that pushes the bag down is equal to:

Where F is the force of a man dragging the bag and mg is gravity pulling the bag down.
The resulting force is:

Normal force has the same intensity but the opposite direction of this force.

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