{"id":278,"date":"2026-06-20T01:13:35","date_gmt":"2026-06-20T01:13:35","guid":{"rendered":"https:\/\/physicsfundamentalsinfo.com\/blog\/?p=278"},"modified":"2026-06-20T01:13:36","modified_gmt":"2026-06-20T01:13:36","slug":"hookes-law","status":"publish","type":"post","link":"https:\/\/physicsfundamentalsinfo.com\/blog\/mechanics\/hookes-law\/","title":{"rendered":"What Is Hooke’s Law?"},"content":{"rendered":"\n
Definition<\/div>

\n

Hooke’s Law states that the force needed to stretch or compress a spring is directly proportional to how far it is stretched or compressed, written as F = kx. Here k is the spring constant (the spring’s stiffness) and x is the extension in metres. The law holds only within the spring’s elastic limit.<\/p>\n<\/p><\/div>\n

Push down on a car’s bonnet and it bounces straight back. Click a retractable pen and feel the tiny resistance under your thumb. Draw a bow and it strains against you \u2014 harder the further you pull. Three different objects, one identical piece of physics underneath.<\/p>\n

That physics is Hooke’s Law: the simple rule connecting how hard you push or pull a springy object to how far it moves. Get it straight and a surprising amount of the world opens up \u2014 kitchen scales, the suspension under your car, even the way atoms wobble inside a solid.<\/p>\n

What Is Hooke’s Law?<\/h2>\n

Picture hanging a weight on a spring. Add one mass and it droops a little. Hang a second, identical mass and it droops twice<\/em> as far. That doubling is the whole idea \u2014 the stretch keeps pace, exactly, with the force.<\/p>\n

Stated precisely: the force F needed to stretch or compress a spring by a distance x is given by F = kx, where k is a fixed number called the spring constant. Plot force against extension and you get a straight line through the origin.<\/p>\n

There’s one catch, and it matters. This tidy proportionality holds only while the spring stays within its elastic limit<\/strong>. Stretch it too far and the rule collapses \u2014 we’ll come back to exactly where and why.<\/p>\n\n \n <\/path><\/marker>\n <\/defs>\n <\/rect>\n A spring stretches in proportion to the load<\/text>\n <\/line>\n <\/line>\n <\/line>\n <\/line>\n <\/line>\n <\/line>\n <\/line>\n <\/rect>\n <\/path>\n <\/circle>\n Natural length<\/text>\n (no load)<\/text>\n <\/path>\n <\/rect>\n m<\/text>\n <\/line>\n F = mg<\/text>\n <\/line>\n unloaded level<\/text>\n <\/line>\n <\/polygon>\n <\/polygon>\n x<\/text>\n extension<\/text>\n F = kx<\/text>\n<\/svg>\n

Hang a mass and the spring extends by x. Double the load and the extension doubles \u2014 the essence of Hooke’s Law.<\/p>\n

A short history<\/h3>\n

The law is named after Robert Hooke (1635\u20131703), one of the sharpest experimental minds of the scientific revolution. He said he had known the relationship since 1660.<\/p>\n

To stake his claim while keeping rivals guessing, he first published it in 1676 as a scrambled Latin anagram, then revealed the answer in 1678: ut tensio, sic vis<\/em><\/a> \u2014 “as the extension, so the force.” Nearly 350 years on, it still underpins every spring scale and clock balance wheel ever built.<\/p>\n

The Hooke’s Law Formula<\/h2>\n

At its core, Hooke’s Law is a single, friendly equation.<\/p>\n

F = kx<\/div>\n

Every symbol earns its place. Here is what each one means, with its SI unit:<\/p>\n