Physics - Young's Modulus

Flashcards

Loading and unloading curves

What is a loading and unloading curve?

loading-unloading-curve-definition

A graph that shows how extension varies with force as a material is being stretched and released.

Why is there a difference between the loading and unloading curves for an elastic band?

loading-unloading-curve-difference

More work is done stretching (loading) the elastic band than releasing (unloading) it.

What is the loop formed between the unloading and loading curves called?

hysteresis-loop-name

A hysteresis loop.

Tensile stress and strain

What is tensile stress?

tensile-stress-definition

The force applied per unit cross-sectional area of a material.

What is the formula for tensile stress?

tensile-stress-formula

\[\sigma = \frac{F}{A}\]

What are the units for tensile stress?

tensile-stress-units

Pascals or $Nm^{-2}$.

What is tensile strain?

tensile-strain-definition

The ratio of the original length of a material to the extension.

What is the formula for tensile strain?

tensile-strain-formula

\[\epsilon = \frac{x}{L}\]

What are the units for tensile strain?

tensile-strain-units

It’s a ratio, so it has no units.

The stress-strain graph

In simple terms, what does this graph show?

stress-strain-graph-meaning

How much a force per unit area will extend an object.

What does $P$ represent?

stress-strain-graph-p-point

The limit of proportionality.

What does $E$ represent?

stress-strain-graph-e-point

The elastic limit.

What do $Y _ 1$ and $Y _ 2$ represent?

stress-strain-graph-yield-points

The yield points.

What does $UTS$ represent?

stress-strain-graph-uts-point

The ultimate tensile strength.

Young’s modulus

What is the Young’s modulus of a material?

youngs-modulus-definition

The ratio of stress to strain for a material.

How can you work out the Young’s modulus from a stress-strain graph?

youngs-modulus-from-graph

It’s the gradient of the initial linear region.

What’s the formula for the Young’s modulus?

youngs-modulus-formula

\[E = \frac{\sigma}{\epsilon}\]

What are the units for the Young’s modulus?

youngs-modulus-units

Pascals or $Nm^{-2}$.

Ultimate tensile and breaking stress

What is the UTS of a material?

uts-definition

The maximum stress a material can withstand before fracture.

What is true about the breaking stress of different objects made from the same material?

breaking-stress-same-material

It is the same.