# An elastic cord is 65 cm long when a weight of 75 N hangs from it but is 85 cm long when a weight...

## Question:

An elastic cord is 65 cm long when a weight of 75 N hangs from it but is 85 cm long when a weight of 189 N hangs from it. What is the spring constant k of this cord?

## Hooke's Law

The extension produced in the spring is directly proportional to the load applied, this statement is called Hooke's law. Mathematically

{eq}\begin{align} F = k x \end{align} {/eq}

where k is called spring constant and depends upon the nature of the material used to make the spring. This law is valid when the force applied is with in the elastic limit. Once the object is stretched beyond its elastic limit, the object will not regain its original configuration on removal of the force exerted. The object gets some permanent set. The stiffness constant or spring constant is expressed in Newton per meter.

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Data Given

• First weight applied {eq}F_1 = 75 \ N {/eq}
• Length of the cord under this first weight {eq}L_1 = 0.65 \ m {/eq}
• Second weight... Hooke's Law & the Spring Constant: Definition & Equation

from

Chapter 4 / Lesson 19
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After watching this video, you will be able to explain what Hooke's Law is and use the equation for Hooke's Law to solve problems. A short quiz will follow.