Classify energy associated with motion, position, deformation and chemical arrangements.
Method and worked examples
Energy is measured in joules, J. Motion gives an object kinetic energy. Height above a chosen reference level gives gravitational potential energy. Deforming an elastic spring or rubber band can store elastic potential energy. Chemical energy is associated with particle arrangements and interactions in substances such as food and fuels.
A stationary object can have potential energy: being at rest does not empty every store. For the same object, higher speed means more kinetic energy; greater height means more gravitational potential energy. Thermal energy involves microscopic motion and interactions. Energy and force are different: use joules for energy and newtons for force.
Example 1
A stationary book is lifted from a floor to a shelf. Which named energy store increases?
Its gravitational potential energy increases relative to the floor.
Example 2
A toy car moves along a level track with its spring already released. Which energy is associated with its motion?
Kinetic energy is associated with the car’s motion.
Watch out:A raised object, stretched spring or fuel can have potential energy even while stationary.
Kinetic and potential energy | Year 8 Science | Ascent Arcade