Hooke's Law

The Physics of Springs

Key Questions

Where does Hooke's Law come from? What does Hooke's Law say about springs? How does Hooke's Law relate to the

conservation of energy?

Where Does Hooke's Law Come From?

Robert Hooke was an English scientist studying all aspects of science (from physics, to biology, to chemistry)

He discovered and created during the 17th century

Famous saying is (in latin): “Ut tensio, sic vis” “As the extension, so the force”

What Does Hooke's Law Say About Springs?

Hooke's Law says this:

F = kx F = Force (Newtons) k = Spring Constant (N/m) x = Displacement (meters)

What Does This Mean?

To summarize his formula, Hooke deduced that every spring has a “spring constant”

This spring constant is a number that tells us how rigid or loose the spring is

The force exerted on the spring to stretch it or compress it is equal to the spring constant times how far it stretched or compressed, in meters.

Practice With Hooke's Law

How much force is required to move a spring that has a constant of 50 N/m .1 meters?

What must be the weight of an object that compresses a spring .5 m if the spring has a constant of 20 N/m?

**What is the spring constant of a spring that compresses by .25 m under a force of 1 N?

Elastic Potential Energy

Elastic Potential Energy is the energy stored in objects such as springs or rubber bands as they compress.

Like all energy, its units are in Joules (J) The equation for Elastic Potential Energy is: EPE = (½)kx²

k = spring constant (N/m)

x = distance spring is compressed from equilibruim

Practice With EPE

**Don't confuse EPE with Gravitational Potential Energy from last unit. Potential energy given to an object by lifting it is often abbreviated as GPE**

How much EPE does a spring have if its constant is 45 N/m and it is compressed .5 m?

How much EPE does a spring have if its constant is 20 N/m and it is compressed 1 m?