Elasticity

Forces can alter an object's size and shape through stretching, compression, or deformation. Load-extension graphs illustrate how elastic materials respond to applied forces, revealing their elastic limits. The spring constant quantifies a spring's stiffness, relating force and extension.

Effects of forces on size and shape

• Forces can cause changes in both the size and shape of an object.

  • Stretching: If a force is applied to a material like a spring or an elastic band, it can cause the object to stretch and change in length.

  • Compression: Forces can also compress materials, making them shorter.

  • Deformation: A force that changes an object's shape without necessarily stretching or compressing it is called deformation. For example, squeezing a ball changes its shape.

Load-extension graphs

• A load-extension graph is used to describe how an elastic solid responds when a force (load) is applied. These graphs are typically used for materials such as springs or rubber bands.

• Experimental Procedure:

  • Load a spring or an elastic material with different weights and measure how much it extends (stretches).

  • Plot the results on a graph with load on the y-axis and extension on the x-axis.

Experimental procedure to produce a load-extension graph.

• Interpreting the Graph:

  • Initially, the graph is typically a straight line, showing that the material obeys Hooke’s Law, which states that the extension is directly proportional to the force applied. There is a constant ratio between force and extension, This is called the elastic region.

  • Beyond the limit of proportionality, the graph may curve, showing that the material is no longer elastic, meaning it has reached its elastic limit and will no longer return to its original shape when the force is removed. The spring or material no longer extends in direct proportion to the applied force.

A load-extension graph.

Spring constant

1. Spring Constant

• Spring Constant (k):

  • The spring constant is a measure of how stiff or strong a spring is. It represents the force required to extend or compress a spring by a unit length.

  • The formula for calculating the spring constant is: