# Materials Flashcards Preview

## Physics > Materials > Flashcards

Flashcards in Materials Deck (15)
1
Q

Hooke’s law

A

The force needed to stretch a spring is directly proportional to the extension of the spring from its natural length provided the elastic limit hasn’t been exceeded

2
Q

Springs in parallel and series

A

For two springs p and q:

In parallel the effective Spring constant = Kp + Kq

In series the effective Spring constant:

1/K = 1/Kp + 1/Kq

3
Q

Elastic limit

A

Point beyond which an object is permanently deformed/stretched

The wire is permanently stretched and suffers plastic deformation

4
Q

Elasticity

A

The ability of a material to be deformed by a force and when the force is removed it will return to its original shape

5
Q

Tensile stress

A

The force per unit cross sectional area

= T/A where T is tension

Unit is pascal (Pa) 1Pa = 1Nm^-2

6
Q

Tensile strain

A

The ratio of extension to length

= dL/L where dL is extension

Strain is a ratio so has no unit

7
Q

Yield point

A

Point at which the stress in a wire suddenly drops when the wire is subjected to increasing strain

8
Q

Ultimate tensile stress/breaking stress

A

Tensile stress required to break a solid material

This measures the maximum stress experienced before breaking not the stress when the object does break

Gives a measure of the tensile strength

9
Q

Brittle material

A

Will snap without any noticeable yield

Little or no plastic deformation prior to failure

E.g. Glass

10
Q

Ductile material

A

The ability of a material to be drawn out under tension reducing the cross sectional area without cracking

For example producing copper wires

11
Q

Limit of proportionality

A

The limit beyond which, when a wire or a spring is stretched, its extension is no longer proportional to the force that stretches it

12
Q

Elastic deformation

A

Once the force has been removed the object will return to its original shape

Atoms move small distances relative to their equilibrium positions but without actually changing their positions - so they are able to return to equilibrium

Occurs as long as the elastic limit hasn’t been exceeded

Work done is stored as elastic strain energy

13
Q

Plastic deformation

A

The material is permanently stretched

The atoms move positions relative to each other and when the load is removed they don’t return to their original positions

Occurs when materials are stretched past their elastic limit

14
Q

Strain energy

A

The work done to deform an object

15
Q

Why is rubber used for aeroplane tyres?

A

It is elastic, the area under the graph between the loading and unloading represents the net output of work that is transferred to thermal energy

This means some of the kinetic energy of the aeroplane is transferred to thermal energy, so the plane doesn’t bounce when landing