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Chapter summary

Presentation: VPfvd

  • The gravitational potential energy of an object is the energy the object has because of its position in the gravitational field relative to some reference point.

  • The kinetic energy of an object is the energy the object has due to its motion.

  • The mechanical energy of an object is the sum of the potential energy and kinetic energy of the object.

  • The unit for energy is the joule (\(\text{J}\)).

  • The Law of Conservation of Energy states that energy cannot be created or destroyed, but can only be changed from one form into another.

  • The Law of Conservation of Mechanical Energy states that the total mechanical energy of an isolated system (i.e. no friction or air resistance) remains constant.

  • The table below summarises the most important equations:

Potential Energy


Kinetic Energy


Mechanical Energy


Physical Quantities


Unit name

Unit symbol

Potential energy (\({E}_{P}\))



Kinetic energy (\({E}_{K}\))



Mechanical energy (\({E}_{M}\))



Table 22.1: Units used in mechanical energy