Final answer:
The object that falls from a 5 m high shelf with 500 J of gravitational potential energy will have 500 J of kinetic energy just before it hits the ground, thanks to the conservation of mechanical energy.
Step-by-step explanation:
When an object with gravitational potential energy falls off a shelf, its potential energy is converted into kinetic energy just before it reaches the ground. Given that the object on the 5 m high shelf has 500 J of potential energy and that it falls off the shelf, we can say that just before the object hits the ground, it has the same amount of kinetic energy as it had gravitational potential energy, ignoring air resistance and other losses.
This is due to the conservation of mechanical energy principle, which states that if only conservative forces (like gravity) are doing work, the total mechanical energy (kinetic plus potential energy) of the system remains constant. Therefore, as the object falls and its height decreases, its gravitational potential energy decreases, but its kinetic energy increases by the same amount.
This means that just as the object reaches the ground, it would have 500 J of kinetic energy, provided there is no energy lost to other forces such as air resistance or friction.