A person wants to determine the spring constant of an exercise stretch cord. He pulls the cord with a force probe that exerts a 55-N force on the cord, causing it to stretch 20cm. Using the Hooke's law find the spring constant of the cord. Assume that the stretch does not exceed the elastic range of the material.

275 N/m

Explanation:

Deduction from Hook's law,

F = ke ... Equation 1

Where F = Force exerted on the cord, k = spring constant of the cord, e = extension of the cord

First we make k the subject of formula in equation 1

k = F/e ... Equation 2

Given: F = 55 N, e = 20 cm = 0.2 m

Substitute in these values into equation 2

k = 55/0.2

k = 275 N/m.

Hence the spring constant of the cord = 275 N/m