Hooke's law and the spring constant

In this lesson

Calculate a spring constant from a force and an extension, and read off a force-extension graph the point where the spring stops obeying Hooke's law.

What it covers

• EXTENSION is the increase in length, not the length: measure the natural length first and subtract, every time, on its own line
• Force = spring constant x extension: quantity, symbol and unit for all three - newtons, newtons per metre, and metres
• Converting centimetres and millimetres to METRES before substituting, on a CONVERT line of its own
• The rearrangements k = F / e and e = F / k, each written out as its own line
• What k MEANS as a rate: the newtons needed for each metre of stretch, so a big k is a stiff spring
• Force-extension graphs: force up the side, extension along the bottom, and a straight line THROUGH THE ORIGIN while Hooke's law holds
• What directly proportional actually means - a ratio that stays the same - and why as the force increases the extension increases is not it
• Reading k as the GRADIENT of that line, with the unit falling out of the two axes
• The limit of proportionality: the load at which the line stops being straight, and finding it on a graph
• Linear and non-linear force-extension behaviour, described in those words
• Compression as well as extension - the relationship behaves the same way
• The boards' own limiter, printed on the atom: this is limited to stationary objects only

Key words

On the specification