First, we can calculate the gravitational potential energy (Ep) using the formula:

Ep = mgh

where:
m = mass (2 kg)
g = gravitational acceleration (10 N/kg)
h = height (3 cm = 0.03 m)

Plugging in the values:

Ep = 2 kg 10 N/kg 0.03 m
Ep = 0.6 J

Therefore, the gravitational potential energy of the object at a height of 3 cm is 0.6 Joules.