Elastic energy! For those who’ve forgotten their school physics –or never paid attention!- elastic energy is potential mechanical energy that can be stored when work is performed to stretch or compress an object or physical system.
How does the frog do it?
As a frog prepares to leap, the calf muscle shortens and pulls on the tendon, which is wrapped tightly around the ankle bone. After a fraction of a second the calf muscle stops moving and the energy is fully loaded onto the stretched tendon. When the frog jumps, the elastic energy is released like a catapult, propelling the frog forward!
Frog fact: Frogs can jump amazing distances -in some cases up to 50 times their body length, which is the equivalent to a human jumping the length of a football field from a standing position!
How does the archer do it?
The archer creates the elastic potential by drawing the bowstring back, changing the configuration of the bow. The force is stored in the distorted shape until the archer decides to release the bowstring, just as the energy is stored in the frog’s tendon until it decides to leap! The arrow is then propelled at a much greater speed than muscles alone could achieve, projecting the arrow much further.
Archer fact: Archers competing in the London Olympics will be aiming their bows at targets approximately 70m away, a distance impossible to reach if they relied on the kinetic energy of the muscles.