# (1)Hooke's Law

- Created by: Olatunde
- Created on: 24-03-14 13:31

First 283 words of the document:

Hooke's Law.

Hooke's Law

Robert Hooke was an English physicist who discovered that the force exerted on a

spring is proportional to the extension of the spring.

He created the equation

F = kx

Where

F = Force

x = Change in length (extension)

k = spring constant

Obeying Hooke's Law

Materials only obey Hooke's Law up to a certain force.

Springs can have different stiffness's. A spring which is stiffer

has a higher spring constant, so a larger force is needed to

extend it.

On a graph of force vs. extension, Hooke's law is obeyed in

the linear region (or straight line region) of the graph.

Be careful some materials do not obey Hooke's Law at all

they are not very stiff.

Elastic and plastic

Elastic deformation is when you stretch a spring or material and it returns to the same

length when you take the force off.

Plastic deformation is when you stretch a spring or material and it does not return to the

same length when the force is removed, so the spring is permanently deformed.

On a graph of force vs. extension, when the material stops behaving elastically and begins to

behave plastically, it is the elastic limit the limit of elastic deformation. After this point we get

the plastic region of the graph.

However, the elastic limit is not the proportionality limit. The proportionality limit is simply the

point where force is no longer proportional to extension and so the graph curves (Hooke's law

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