# An elastic cord is 61 cm long when a weight of 75 N hangs from it but is 85 cm long when a weight of 210 N hangs from it. What is the "spring" constant #k# of this elastic cord?

##### 1 Answer

Mar 11, 2017

#### Answer:

The spring constant is

#### Explanation:

Let the length of the elastic cord at rest

Therefore,

In the first case,

In the second case,

We have 2 equations with 2 unknowns.

So,