Final answer:
The normal force of a block with mass 28 kg on a horizontal surface is equal to the gravitational force on the object, which is calculated as the mass times the acceleration due to gravity. Thus, the normal force is 274.4 N.
Step-by-step explanation:
To calculate the normal force of a block on a rough surface, we need to understand that on a horizontal surface, the normal force is equal to the gravitational force acting on the object when there is no vertical acceleration. Given a mass of 28 kg (ignoring the typo of the block with mass g), and assuming the acceleration due to gravity is 9.8 m/s² (the standard on Earth's surface), the gravitational force on the block is mass times the acceleration due to gravity. Hence, the gravitational force (weight) of the block is 28 kg × 9.8 m/s², which is 274.4 N.
Since there are no other vertical forces, the normal force exerted by the surface on the block is also 274.4 N to balance the weight of the block, ensuring no vertical motion.