# Physics - Recall for Chapter 6: Materials

> Source: https://ollybritton.com/notes/a-level/physics/recall-questions/chapter-6-materials/ · Updated: 2021-08-03 · Tags: physics, materials, school, recall-questions

## Recall Questions
##### Define Hooke's law??
The extension of a spring is directly proportional to the force applied, provided the elastic limit of the spring is not exceeded.

##### Define extension??
The difference between the final and initial length of an object.

##### Define elastic deformation??
The material returns to its original shape and size after any applied forces are removed.

##### Define plastic deformation??
The material will not return to its original shape and size after any applied forces are removed. It has been permanently deformed.

##### Define the elastic limit of a material??
The point beyond which a material becomes permanently deformed and does not return to its original shape and size after any applied forces are removed.

##### What is the area under a force-extension graph equal to??
The work done by the force.

##### Define tensile stress??
The force per unit cross-sectional area.

##### Define tensile strain??
The extension (or compression) of an object divided by its original length.

##### Define the Young modulus of a material??
The Young modulus is the tensile stress divided by the tensile strain.

##### Define the limit of proportionality of an object??
The point up to which an object's stress and strain are proprtional to each other.

##### How can the Young modulus of a material be found??
From the gradient of the initial straight-line section of the object's stress-strain graph.

##### What does the area under the straight-line section of a material's stress-strain graph represent??
The energy stored in the material per unit volume.

##### Define the breaking stress of a material??
The value of the stress at which the material snaps or breaks.

##### Define the ultimate tensile stress (UTS) of a material??
The maximum stress thye material experiences.

##### What type of materials have a high Young modulus??
Stiff materials.

##### What type of materials have a high ultimate tensile stress and breaking point??
Strong materials.

##### What is meant by a ductile material??
A material that undergoes significant plastic deformation after deforming elastically.

##### What is meant by a brittle material??
A material that snaps after deforming elastically and does not deform plastically.

##### What is meant by a polymeric material??
A material of long-chain moleculues that will deform elastically.

##### What is an example of a ductile material??
Metal used for making wires.

##### What is an example of a brittle material??
Glass or cast iron.

##### What is an example of a polymeric material??
Rubber.

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