Potential energy is the energy an object has based on its position relative to a reference position; the energy is stored in the object. The two most common types of potential energy are gravitational and elastic–both are measured in Joules.
Gravitational potential energy is the energy an object has as the object is raised or lowered with respect to a reference level.
The Equation of gravitational potential energy is: PEg = mgh
(g = acceleration due to gravity = 9.8 m/s2)
What is the Potential energy of a 2kg apple on a branch 4 meters above the ground?
PEg = mgh = (2)(9.8)(4) = 78.4 J
Elastic potential energy is the energy an object has when it is stretched or compressed from its normal rest or equilibrium position. Elastic objects have a spring constant k (measured in N/m), which describes how much force is needed to stretch or compress the elastic object.
The equation for elastic potential energy is: PEs = one half 1 2 kx2
What is the potential energy stored in a 1000 N/m spring that is compressed .03 m?
PEs = one half 1 2 kx2 = (.5)(1000)(.03)2 = 0.45 J