# If the length of a 29 cm spring increases to 47 cm when a 15 kg weight is hanging from it, what is the spring's constant?

$= 833.33 N {m}^{-} 1$
$F = k x$
force $F = m g = 15 \times 10 N = 150 N$
$g = 10 m {s}^{-} 2$
Increase in length $l = \left(47 - 29\right) c m = 18 c m = 0.18 m$
force constant $k = \frac{F}{x} = \frac{150}{0.18} \frac{N}{m} = 833.33 N {m}^{-} 1$