Hooke's Law

Hooke’s law

ΔF = kΔx

Spring constant symbol

k

What does the spring constant tell you

The stiffness of the spring

Extension symbol

Δx

What force acts on the support of a wire with a weight on

The third law pair of the force on the wire

Why don’t other materials fully with Hooke’s law

k has a different value depending on whether the forces are tensile or compressive

What is special about a spring

It changes length when a pair of opposite forces are applied

What materials does Hooke’s law apply to

Most of them, up to a point

Tensile forces

Forces stretching the spring

What force do tensile forces create

Tension

Compressive forces

Forces squashing the spring

What force do compressive forces create

Compression

Limit of proportionality

The point at which materials stop obeying Hooke’s law

Elastic limit

The point at which the material becomes permanently stretched

What occurs first- the limit of proportionality, or the elastic limit

Limit of proportionality

Which type of deformation occurs before the elastic limit

Elastic deformation

Which type of deformation occurs after the elastic limit

Plastic deformation

Explain elastic deformation

Atoms move relative to their equilibrium positions, without changing position in the material such that once the load is removed, atoms return to their equilibrium positions

Explain plastic deformation

Atoms move relative to one another such that when the load is removed, they don’t return to their equilibrium positions

Experiment to investigate extension

1- Attach a clamp to a spring, ruler and a clamp stand.

2- Measure the natural length of the spring, then attach a weight and record the extension

3- Plot a graph of force against extension

4- The gradient of the graph is k

Risks and preventions of the Hooke’s Law experiment

-Wear goggles in case the object snaps

-Make sure you are standing up so you can get out of the way if the weights fall