Gravitational potential energy and kinetic energy — FAQ

Kinetic energy is the energy an object possesses due to its motion, depending on its mass and speed. Gravitational potential energy is stored energy due to an object's position (height) in a gravitational field, dependent on its mass, height, and gravity.

Assuming negligible air resistance simplifies calculations, allowing us to apply the principle of conservation of mechanical energy directly, equating GPE and KE changes without accounting for energy loss to heat. It provides an idealized model to understand the core concepts.

Yes, GPE can be negative. This happens when the object's position is below the chosen reference point (where $h=0$). For instance, if you define the ground as $h=0$, an object in a deep pit below ground level would have negative GPE relative to the ground.

The work-energy theorem states that the net work done on an object is equal to the change in its kinetic energy ($W_{net} = \Delta KE$). This is a fundamental link between work (a transfer of energy) and kinetic energy (the energy of motion).