# If the length of a 23 cm spring increases to 40 cm when a 7 kg weight is hanging from it, what is the spring's constant?

Mar 14, 2018

$k = 4035.29$ kg/s^2

#### Explanation:

Hooke's Law: $F = - k x$

$F = m g$ ; $m = 7$ kg and $g = 9.8$ N
k = ?
$x = 40 - 23 = 17$ cm $= 0.17$m

The negative sign is simply for directionality. We only care about magnitude here.

$k = \frac{m g}{x} = \frac{\left(7\right) \left(9.8\right)}{0.17} = 4035.29$ kg/s^2