Determine the potential energy of a spruce cone weighing 20 g hanging on a tree at a height of 45 m from the ground.

By definition, the potential energy of a body of mass m in the gravitational field of the Earth is described by the equation: E = m * g * h where E is the potential energy, m is the mass of the body, g is the acceleration of gravity, h is the height of the body relative to the surface. Then we get:
E = 0.02 * 10 * 45 = 9 J.