What is:

- Tensile Deformation
- Compressive Deformation
- Elastic Deformation
- Plastic Deformation
- Elastic Limit

Tensile Deformation: Changes shape under tension.

Compressive Deformation: Changes shape under compression.

Elastic Deformation: Goes back to its original shape.

Plastic Deformation: Permanent change in shape.

Elastic Limit: Stretched beyond the elastic limit, causes plastic deformation.

What is the equation for **HOOKE'S LAW?**

F = kx

k is the **spring constant**

k = F ÷ x

^^^^^^^^

Gradient of a Force vs Extension graph.

State **HOOKE'S LAW.**

The extension of a spring is directly proportional to the force applied.

This is true as long as the elastic limit of the spring has not been exceeded.

What is this?

A hysteresis loop.

What **DOES NOT** obey **HOOKE'S LAW?**

Rubber bands do not obey Hooke's Law.

What is the equation for **STRESS **and what are its **UNITS?**

σ = F ÷ a

Units : Nm² or Pa

What is the equation for **STRAIN **and what are its **UNITS?**

Σ = Extention ÷ Original Length

Σ = x ÷ L

Strain has no units, it is a ratio or a percentage.

State what each point on the graph represents.

P : Limit of proportionality - Hooke’s Law no longer obeys at this point.

E : Elastic limit.

Y1 & Y2: The yield point - The wire is about to give

UTS (Ultimate Tensile Strength) : Stress at its limit - About to break - The wire begins to thin out.

What is the equation for **THE YOUNG MODULUS **and what are its **UNITS?**

σ ÷ Σ

Stress ÷ Strain

Units: Pa or Nm²

How do you calculate the **GRADIENT **on a **STRESS vs STRAIN GRAPH?**

σ ÷ Σ

The Young Modulus is the gradient, which relates to te stiffness of the material.

What is the equation for **ELASTIC POTENTIAL ENERGY?**

½Fx

For a spring that obeys Hooke's Law:

F = ½kx²