The physics of archery
Have you ever thought of how a bow actually shoots out an arrow. At first appearance it looks so simple but the underlying laws of physics are incredible. Archery is all about energy and the transference of it from one object to another.
Lets consider a recurve type bow as it is simple to understand rather than the complexities of a compound bow. That being said, a compound bow operates under the exact same laws of physics, but introduces cams and mods as a force multiplier. For the sake of simplicity, let’s study the recurve bow.
The limbs of all bows are essentially springs and when deformed, want to return to their original position. This principle is called elasticity. Elasticity is the ability of a body to resist distorting influence and return to its original size and shape when that influence or force is removed. However, all materials have limits to the degree of distortion they can endure without breaking or irreversibly altering their internal structure. That is why when you deform the limbs beyond their limits they will break/fracture or be permanently damaged and lose their elasticity.
When you draw a bow string back, you don't stretch the string, you change the shape of the bow by distorting the limbs from their original position. When you remove the force by either letting loose the bow string , or “letting down” on the bow string, the limbs return to their original shape.
When you use the muscles in your arms and your back to draw the bow string backwards you transfer a exerting force from your body into the bowstring. The bow string then deforms the limbs by bending them from their original position. Holding the bow string steady at full draw maintains that limb distortion generating elastic energy (also called “mechanical potential energy” or simply “potential energy”) which is the energy available in the bow limbs at that very moment.
The next concept is kinetic energy or “energy in motion”. Kinetic energy is a form of energy that an object (ie: the arrow) has by reason of it’s motion.
When you release the bow sting at full draw with an arrow knocked, the potential energy that you generated by deforming the limbs is converted into kinetic energy when the limbs snap back to their original shape under the principal of elasticity. The kinetic energy released by the limbs snapping back to their original shape transfers into the bow string, the bow string then transfers the kinetic energy into the nocked arrow propelling it forward. However, not all the kinetic energy is absorbed by the arrow with some of the kinetic energy feeding back into the bow as vibration/oscillation, heat and sound.
Stabilisers and limb dampeners affixed to modern bows are items designed to absorb that small amount of kinetic energy vibration and oscillation that was not absorbed by the arrow but fed back into the bow. The ‘smoothness’ of a bow is a measure in part, of how much kinetic energy is fed back into the bow and felt as vibration and oscillation.