Final answer:
When the brick is sitting on the shelf, it has gravitational potential energy of 392 J.
Step-by-step explanation:
When the brick is sitting on the shelf, it has gravitational potential energy. Gravitational potential energy is the energy that an object possesses due to its height above the ground. The formula to calculate gravitational potential energy is P.E. = mgh, where m is the mass of the object, g is the acceleration due to gravity (approximately 9.8 m/s²), and h is the height above the ground. In this case, the mass of the brick is 5 kg, the height is 8 m, and the acceleration due to gravity is 9.8 m/s². Plugging these values into the formula, we get P.E. = (5 kg)(9.8 m/s²)(8 m) = 392 J (joules).