Robert Hooke was a British physicist who stated that there is a proportional relationship between the force required to extend or compress a spring, and the distance that the spring is extended or compressed. This relationship is expressed by the equation F = kx where F is the force, k is the spring’s stiffness (a constant), and x is the distance.
Two of the most common types of springs are compression and extension springs. These helical mechanisms are most often made of metal, but occasionally are made of other materials as well. Extension springs are coiled more tightly than compression springs, while both may have hooks or loops on either end to attach to other objects. The “compression” and “extension” names refer to the state in which the springs contain the most potential energy.
The springs used on trampolines are an example of extension springs. They are naturally at rest in a tightly coiled, compressed position, contain the most potential energy when someone steps onto the trampoline and extends them, and they release that energy as they tighten up again (pulling the canvas taut and flinging the jumper into the air).
Torsion springs are wound tightly like an extension spring, although the ends of the spring typically extend away from the spring in a non-helical shape. Instead of being compressed or extended, a torsion spring is twisted to store potential energy. Common applications of torsion springs are those found in clothespins and in traditional mouse traps. Torsion springs obey Hooke’s Law, but it is an angular form (𝞽 = kθwink of the equation rather than linear. For torsion springs, torque replaces force, and angular distance in radians replaces linear distance.