# If the length of a #45 cm# spring increases to #63 cm# when a #7 kg# weight is hanging from it, what is the spring's constant?

##### 1 Answer

Jun 11, 2018

Approximately

#### Explanation:

We use Hooke's law, which states that,

where:

#F# is the force applied in newtons

#k# is the spring constant in#"kg/s"^2# or#"N/m"#

#x# is the extension in meters

Here, the force is the weight of the object, which is equal to:

The spring constant is then: