Short Notes:

Springs are mechanical devices that stretch and compress according to a simple law. First formulated in 1678 by English physicist Robert Hooke, this law, appropriately called Hooke's law, states that springs deform proportionally to the forces acting on them. Simply put, the greater the force pulling or pushing on a spring, the farther the spring will stretch or compress. Beyong a certain point known as the elastic limit, the bonds that link the spring's atoms will shift and permanently distort the spring, which will never recoil again.

The elasticity of springs makes them useful in scales and balances. A comparison between how much a spring is stretched by an unknown weight and a known weight makes it easy to calculate the unknown weight.

Spring and forces: A spring will always stretch the same distance when subjected to the same force. If the person applying a force (F) and the block applying a weight (W) stretch the spring equally far, the force must equal the weight.

An ordinary coil spring is a torsion spring. As a force is applied to the spring and the spring stretches, the wire twists. This twisting strains the bonds that connect the individual atoms within the spring, changing the distance between the atoms. As soon as the distorting force is removed, atoms return to their original positions, restoring the spring to its original shape.

Elasticity: The atoms in a metal spring act as if they were connected by springs. When compressed, the atoms' tendency is to push back to their normal position. When driven apart, they tend to pull back toward each other, restoring the metal's original shape. If the atoms stretch beyond their elastic limit, the bonds connecting them break, and the metal is bent permanently into a new shape.