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Energy Transfer

Elastic Potential Energy and Restoring Force.

What is Elastic Potential Energy?

Elastic Potential Energy called "EPE" is a measure
of the restoring force when an object changes its shape.
Elastic means that an object
will return to its original shape when the force is removed.

EPE is similar to GPE except that the restoring force
depends on the substance of the material and not gravity.

For example, if we stretch a spring and then let go,
it will return to its original shape
if it has not been stretched beyond its elastic limit.
The force that returns the spring to its original shape
is called the restoring force.

What is the Size of the Restoring Force?

The size of the restoring force depends on the
stiffness of the spring (called the spring constant)
and the amount that the spring
has been stretched (called the extension).

Restoring force = spring constant x extension.

F = k x e

Where F is the force in Newtons (N)
k is the spring constant in Newtons per metre (N/m)
e is the extension in metres (m).

The more stiff the spring and the further
it has been stretched, the more EPE it has gained.

Anything elastic will gain EPE
when its shape is forced to change.

Other examples of Elastic Potential Energy are

1. A ball when it bounces on the ground.

2. A catapult pulled back to launch a stone.

3. A crossbow primed to fire an arrow.

When the shape is restored
EPE is transferred to Kinetic Energy  ( + heat ).

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