Understanding the Concepts

* Potential Energy: An object at a height has potential energy due to its position in Earth's gravitational field. This energy is calculated as: PE = mgh, where:

* m = mass (kg)

* g = acceleration due to gravity (9.8 m/s²)

* h = height (m)

* Kinetic Energy: As the object falls, its potential energy is converted into kinetic energy, the energy of motion. This is calculated as: KE = 1/2 * mv², where:

* m = mass (kg)

* v = velocity (m/s)

Solving the Problem

1. Calculate the potential energy:

PE = (20 kg) * (9.8 m/s²) * (30 m) = 5880 J

2. Since energy is conserved, the potential energy at the top is equal to the kinetic energy just before impact:

KE = PE = 5880 J

Answer: The object will have 5880 joules of kinetic energy just before it hits the ground.