**Hooke’s Law **

- $F = -k \Delta x$
- States that within the limit of proportionality, the extension produced in a material is directly proportional to the load applied
- SI unit of k: Nm
^{-1} - $\uparrow$ k( Higher stiffness), $\downarrow$ extension
- Applies to springs, elastic springs and metals in form of wires

Springs connected in **parallel**

$k_{eff} \, = \, k_{1} + k_{2} + \, …$

Springs connected in **series**

$\frac{1}{k_{eff}} = \frac{1}{k_{1}} + \frac{1}{k_{2}} + \, …$

- Same load, less extension compared to series

Elastic potential energy stored in wire or spring (Amount of work stored)

$W = \frac{1}{2} k_{eff} X^{2}$

In the equation you wrote F = -kx,should ‘k’ be negetive ?