1. Energy

2. Nature of Energy
Energy is all around you.
You hear energy as sound, you see energy as light, you can feel energy in wind.
Living organisms need energy for growth and movement.
You use energy when you hit a tennis ball, compress a spring, or lift a grocery bag.
Energy is the ability to do work. It is measured in Joules (J)

3. There are two states of energy:
Potential and Kinetic

4. Potential Energy A stretched rubber band has energy.
Two magnets, when pulled apart, have energy.
The rubber band has energy because it’s stretched rather than relaxed.
The magnets have energy because they’re apart rather than together.

5. Potential Energy
When something, or a group of things, has energy simply because of relative position or shape, it’s known as potential energy…(stored energy).
A stretched rubber band has PE and thus the ability to do something…
snap back into place if you let go.
Two separated magnets have PE and thus the ability to do something…
jump back together when you let them go.

6. Potential Energy
Gravitational Potential Energy (GPE) – the PE everything has because of its height above the Earth’s surface.
GPE = m g h (where m equals the mass of the object, g equals 9.8 m/s2, and h equals the height of the object above some surface)

7. Kinetic Energy
Anything that is moving has a special kind of energy known as “moving energy.”
This “moving energy” is called kinetic energy.
A rolling ball, a running dog, a falling object, two magnets heading towards each other, and anything else in motion, all have kinetic energy.
The faster the object moves, the greater the kinetic energy.

8. Kinetic Energy
Two factors that affect kinetic energy are mass and velocity.
KE increases as mass increases.
KE increases as velocity increases.
Kinetic energy = ½ mass x velocity2
KE = ½ mv2

9. The most common energy conversion
Energy Conversions
The most common energy conversion
involves the changing of potential energy into kinetic energy or vice-versa.

10. 1 2 3
At the top of the ramp, the marble’s ME is equal to PE because the marble has no velocity.
100% PE
As the marble goes down the ramp, it loses height but gains speed. The PE lost is equal to the KE gained.
50% PE & 50% KE
As the marble speeds along the bottom of the ramp, all of the PE has changed to KE. Total ME remains unchanged.
100% KE

11. Energy Conversions
All forms of energy can be converted to other forms.
Law of Conservation of Energy – energy cannot be created or destroyed.
No matter how energy is transformed or transferred, all of the energy is still present somewhere in one form or another.
As long as you account for all of the different forms of energy involved in any process, you will find that the total amount of energy never changes.

12. Questions What is energy?
Can energy be transferred from one object to another?