Materials Flashcards
What are tensile forces ?
Forces that produce an extension
What are forces that shorten an object called?
Compression forces
A straight line in a force extension graph means what?
The spring undergoes elastic deformation. This means that the spring will return to its original length when the force is removed.
When the force extension graph doesn’t have a constant gradient what does that mean?
The spring undergoes plastic deformation- permanent changes to the structure of the spring, it doesn’t return back to its original length.
What is hooke’s law
The extension of the spring is directly proportional to the force applied.
This is true as long as the elastic limit is not exceeded
What is the force constant, k?
A measure of the stiffness of a spring.
What will a spring with a large force constant be like?
It will be hard to extend ( a stiff spring)
How do you find force constant from a force-extension graph?
The gradient
When can work done be fully recovered?
When a material doesn’t go beyond its elastic limit.
When can the work done not be fully recovered?
When the material has gone through plastic deformation.
How do you calculate the work done from a force-extension graph?
The area under the graph
How do you calculate elastic potential energy?
E=1/2Fx
For a spring that obeys hooke’s law what is the elastic potential energy?
E=1/2kx²
What is the relationship between elastic potential energy and extension?
E is directly proportional to extension²
Metal wires under tensile forces
The loading curve will obey Hooke’s law until the elastic limit. The wire will be longer then it was at the start as the wire suffered from plastic deformation.
