# If the length of a #21 cm# spring increases to #37 cm# when a #7 kg# weight is hanging from it, what is the spring's constant?

##### 1 Answer

Apr 10, 2018

#### Answer:

I get

#### Explanation:

We use Hooke's law, which states that,

#k# is the spring constant in newtons per meter

#x# is the extension of the spring in meters

So here, we got:

The force is the weight of the weight thingy, which is

And so,