1. Chapter 9
Energy

2. The Big Idea Energy can change from one form to another
without a net loss or gain.

3. Discussion What is energy? Pros and cons?
How many different forms of energy can you think of?
Take 1 minute with an elbow partner and write down as many things you know about energy

4. Energy may be the most familiar concept in science, yet it is one of the most difficult to define.
Persons, places, and things have energy, but we observe only the effects of energy when something is happening.
Only when energy is being transferred from one place to another or transformed from one form to another.

5. Work! work = net force X distance
When you apply a force on an object and it moves, you’ve done work.

6. Units of Work Remember Work = Force x Distance.
What are the units for work?
Newton x meters
1 Nm = 1 Joule (J)

7. Power
Power equals the amount of work done divided by the time interval during which the work is done.

8. Units for Power Remember Work is measured in Joules
Power is measured in
Joules per Second

9. Mechanical Energy
The energy due to the position of something Or the movement of something.
The two forms of mechanical energy are kinetic energy and potential energy.

10. Potential Energy 3 kinds Elastic Potential Energy Chemical Energy
A stretched or compressed spring
A stretched rubber band
A bow in a bow and arrow
Chemical Energy
Is released when a chemical change takes place.
Gravitational Potential Energy
Energy of position in a gravitational field.

11. Gravitational Potential Energy
Focus on this type of potential energy.
gravitational potential energy
= weight X height Or
PE=mgh

12. Kinetic Energy Energy of motion Or
Kinetic energy = 1/2 mass X velocity squared Or

13. Total Mechanical Energy
the total Mechanical energy
Add the Kinetic and potential energy
ME = KE + PE
Let’s think about the units.

14. Try it. An object has a mass of 10kg. It is 5m off the ground.
It is moving 2m/sec.
Find its gravitational potential energy.
Find its kinetic energy
Find its total mechanical energy

15. Simple Machines
A machine transfers energy from one place to another or transforms it from one form to another.
A lever is a simple machine made of a bar that turns about a fixed point.
The fulcrum is the fixed point that a lever operates on.

16. Mechanical Advantage. work input = work output
The ratio of output force
to input force for a machine
is called the
mechanical advantage.

17. Try it!
Find the mechanical advantage.

18. Conservation of Energy
Energy can neither be created nor destroyed, it is only changed from one form to another.

19. Work Energy Theorem Anytime Work is done energy changes.
We are going to think of this in terms of kinetic energy.
Work = KE (Kinetic Energy)