Hookes law states that the extension of a

Hooke’s law states that the extension of a spring force is proportional to the force used to stretch the spring. F∝x ‘Proportional’ means that if the force is doubled then the extension also doubles. The line on a graph of force against extension will be a straight AND go through the origin.

Springs the force required to stretch it the change in its length F = kx k=the spring constant

Force (N) Force against extension graph 0 0 Extension (mm)

Does a larger k value mean that a spring is A. easier to stretch, or B. harder to stretch?

Elastic limit Up to a certain extension if the force is removed the spring will return to its original length. The spring is behaving elastically. If this critical extension is exceeded, known as the elastic limit, the spring will be permanently stretched. Hooke’s law is no longer obeyed by the spring if its elastic limit is exceeded. The right hand spring has been stretched beyond its elastic limit

Force (N) Force against extension graph if the elastic limit is exceeded elastic limit 0 0 Extension (mm)

Ex: 2 N If a spring stretches by 20 cm when you pull horizontally on it with a force of 2 N, what is its spring constant? How far does it stretch if you suspend a 2 N weight from it instead? 2 N

Hooke’s Law lab SPP (Short Sharp Practical) spring Aim: Determine the spring constant (k) for a single spring by finding the gradient from a graph of F (N) vs x (m). Use masses 50 g to 250 g, let g = 10 ms-2 weight s pin metre rule

Choose appropriate words to fill in the gaps below: stretched the Hooke’s law states that when a wire or spring is _____ increase in length or extension _____ is proportional to the load ______ applied. force This law is not obeyed if the spring is taken beyond its ______ elastic limit after which it will become permanently _______ stretched. A ____ rubber band does not obey Hooke’s law. A graph illustrating Hooke’s law will have a line that is origin straight ______ and passes through the _______. WORD SELECTION: stretched origin elastic force permanently rubber extension straight

Spring Potential Energy, Ep x F = kx F kx Work 0 x