An extension spring is a type of mechanical spring designed to absorb and store energy when stretched. It is made of coiled metal and works by pulling apart, creating tension. These springs are commonly used in various applications, such as in garage doors, trampolines, and clotheslines, where they help to provide resistance and support. The design of an extension spring typically includes hooks or loops at both ends, allowing it to be easily attached to other components. When a force is applied, the spring elongates, and when the force is removed, it returns to its original shape. This property makes extension springs essential in many mechanical systems.