Elastic Potential Energy (Sec 3.4)
Elastic potential energy is the energy stored in a material when it is stretched or
compressed. If the material is elastic, this energy can be returned to the system, but
in inelastic materials, permanent change occurs once the force applied to the object is
removed.
Hooke’s Law
Hooke’s law states that the force applied to an object is directly proportional to the
spring’s extension.
Hooke's Law and Elastic Potential Energy
→Graph must pass through (0,0)
→Stiffer springs have a greater spring constant. (Larger gradient)
→Not obeyed after elastic limit (break in linearity)
F
=−
kx
EPE
=
Area
=1
2
Fx
=1
2
k x
2
i. Calculate spring constant of red and yellow springs.
ii. Calculate energy stored in red and yellow when extended
0.1 metres.
k = spring constant (Nm-1) = Gradient of
graph
x = change length (m) Extension or
Compression
F = force applied (N)
EPE = elastic potential energy (J), energy
stored in spring/object = Area under graph
