Elastic Potential Energy
Elastic Potential Energy (EPE) is a measure of the restoring force when an object changes its shape
Compression and Extension It takes force to press a spring together. More compression requires stronger force. extend It takes force to extend a spring. force More extension requires stronger force.
Stretched or Compressed Elastic potential is gained whether the spring is stretched or compressed
Change in Potential Energy The distance (x) stretched or compressed determines the change in potential energy of the spring
Meaning of Elastic Elastic means the object will return to its original shape when the force is removed.
Hooke ’ s Law The force from the spring attempts to restore the original length. This force is called the restoring force. This is also called Hooke’s law. L+ x L - x L
Scales One common use for a spring is to measure weight. The displacement of the spring measures the mass. -y F g = -mg F s = -k(-y)
Other Forms of Elastic Potential A ball when it bounces on the ground A catapult pulled back to launch a stone A crossbow ready to fire an arrow
EPE to GPE Conversion/Conservation A 30 kg child pushes down 15 cm on a trampoline and is launched 1.2 m in the air. Elastic potential energy is created by the stretch of the trampoline. Then the child has all kinetic energy, which becomes all gravitational energy at the top of the jump. The energy is conserved.