Final answer:
A 40 kg person sitting on the ground has a gravitational potential energy of zero because their height above the reference point (ground level) is zero.
Step-by-step explanation:
To calculate the gravitational potential energy (GPE) of a person sitting on the ground, we can use the formula GPE = mgh, where m is mass, g is the acceleration due to gravity, and h is the height above a reference point.
For a person sitting on the ground, the height h is effectively zero, and therefore the gravitational potential energy is also zero, regardless of the mass of the person.