6.16 - Transfer Between KE & GPE

Falling and rising transfer energy between two stores

• When an object falls, energy is transferred from its gravitational potential energy store to its kinetic energy store - it loses height and speeds up.
• When an object rises - thrown upwards or rolled up a slope - the transfer runs the other way, from its kinetic energy store to its gravitational potential energy store - it slows down as it gains height.

Energy conservation between the stores

With no air resistance

With no air resistance, none of the energy escapes to other stores, so the amount lost from one store equals the amount gained by the other:

Energy lost from gravitational potential energy store = energy gained by kinetic energy store

Air resistance transfers energy away

• As an object moves through the air, air resistance transfers some energy to the thermal energy stores of the object and the surrounding air.
• The kinetic energy store therefore gains less energy than the gravitational potential energy store loses.