Chapter 3.4 - Materials Flashcards
Elasticity
The property of a body to return to its original shape once the deforming force is removed
Deformation
The change in shape or size of an object
Elastic Deformation
An object that deforms that will return to its original shape once the deforming force is removed
Plastic Deformation
When an object deforms and then when the deforming force is removed the object remains deformed
Tensile force
Creates tension in an object and will result in an extension
Compressive force
A force that causes an object to compress
What a force extension graph will look like for a metal
Will start of straight. Then the limit of proportionality is reached and the gradient will start to change. Then the elastic limit is reached and it will extend more per unit force (gradient decreases) until it reaches the point of fracture
Experiment to observe force-extension of a wire
Clamp a wire on one end of a table and attach a weight on the other end. The weight should dangle off the table and the wire should be placed over a pulley. Attach a marker to the wire and fix a ruler in position. Add more mass to the weight and record how much the wire extends
Hookes Law
The extension of an object is proportional to the force that causes it, provided that the elastic limit is not exceeded
Force constant of a spring
The force required to extend the spring by one unit length
Hookes law in equation form
F=kx
Area under a force-extension graph
Work done to stretch the object
What happens to the work done put into stretching a wire that exceeds its elastic limit
- At first the work done is causing an increase in elastic potential energy
- Once the material has exceeded its elastic limit the rest of the energy that is input will be converted to heat
Stress
Force per unit cross sectional area
Strain
Extension per unit length