Transcript The Law of Conservation of Energy

The Law of Conservation of Energy:
The Law of Conservation of Energy:
● The Law of Conservation of Energy states that energy cannot
be created nor destroyed.
● Energy can be transformed from one form into another, but
the total amount of energy never changes.
The Law of Conservation of Energy:
Mechanical energy transformations:
● When water is behind a dam, it has potential energy. The potential energy of the
water changes to kinetic energy in the movement of the water as it flows over the
dam.
● When a rubber band is stretched, kinetic energy is transformed into potential
energy. The further back you stretch the rubber band, the greater potential energy,
and the more energy that will be transferred as kinetic energy. When a stretched
rubber band is released its potential energy is transformed into kinetic energy as
the rubber band moves.
● When a book is lifted to a shelf, kinetic energy is transformed into potential
The Law of Conservation of Energy:
Mechanical energy transformations:
● When a book is lifted to a shelf, kinetic energy is transformed into potential
energy. If the book falls off the shelf the potential energy is transformed to kinetic
energy.
The Law of Conservation of Energy:
Energy is conserved during energy transformations:
● Transformations may occur between any of the various types of energy but energy
itself is never lost.
● The potential energy that a book on a shelf has is from the kinetic energy it took to
lift the book to the shelf.
The Law of Conservation of Energy:
● A swing pendulum (such as a Newton’s cradle) also demonstrates how energy is
conserved as it changes forms.
○ Kinetic energy is used to pull a ball back; this energy is transformed into
potential energy.
○ The ball is released and the ball swings back toward the other three balls
(kinetic energy).
○ The moving ball strikes the stationary ball and the kinetic energy is
transferred from one ball to the next.
The Law of Conservation of Energy:
○ The last ball swings away from the others because of the kinetic energy that
was transferred to the ball.
○ If this experiment is repeated by pulling back two balls, then two balls will
swing off of the other end.
○ This shows conservation of energy because one ball has enough potential
energy to cause one ball to move; two balls cause two to moves, and so on.
The Law of Conservation of Energy:
● Although energy is not lost during energy transformations, some is transformed
into heat and friction. This means that all of the potential energy stored in a book
is not going to be transformed into kinetic energy.
The Law of Conservation of Energy: