1. Energy can change from one form to another without a net loss or gain.

2. Physics Standard SP3
Students will evaluate the forms and transformations of energy.
a. Analyze, evaluate, and apply the principle of conservation of energy and measure the components of work-energy theorem by
• describing total energy in a closed system.
• identifying different types of potential energy.
• calculating kinetic energy given mass and velocity.
• relating transformations between potential and kinetic energy.
b. Explain the relationship between matter and energy.
c. Measure and calculate the vector nature of momentum.
d. Compare and contrast elastic and inelastic collisions.
e. Demonstrate the factors required to produce a change in momentum.
f. Analyze the relationship between temperature, internal energy, and work done in a physical system.
g. Analyze and measure power.

3. How does the popping frog get its energy?
Place the frog on the desk and observe what happens when you push on the tab and gently release it.
What happens when you apply more force?
What propelled the frog into the air?
What is the best way to launch the frog for maximum distance?
What is the best way to launch it for maximum height?
Describe where the frog got the energy to move upward and downward through the air.

4. What propelled the frog into the air?
Elastic potential energy is transferred into kinetic energy

5. Describe where the frog got the energy to move upward and downward through the air.
The work you do to launch the frog
Gravitational energy makes everything fall!

6. WORK
Work is the product of the force on an object and the distance through which the object is moved.
Work = Force x Distance

7. Work is done if tow conditions are met.
A force acts on an object
And the object moves

8. Two Categories of Work
1. Work done against another opposing force Example; Lifting vs Gravity
What are the opposing forces in the following; Sliding a box across the floor Shooting a rubber band Inflating a tire

9. 2. Work is done to change the speed of an object

10. W= Fd
Work = force x distance

11. The unit for work is the Joule
1 Joule = the work done when 1 newton of force is used to move an object 1 meter
Kilojoules = thousands of joules
Lifting an apple over your head
Megajoules = millions of joules
Stopping a truck traveling 100km/hr

12. What happens when you do work on sand?
Measure the temperature of the sand.
Remove the thermometer and cover the hole. Shake the sand vigorously for one minute.
Measure the temperature of the sand again.
What happened to the temperature of the sand?
How can you explain the change in temperature of the sand in terms of work and energy?

13. Power
The rate at which work is done.
Power = work done/time interval

14. Power is measured in Watts
One watt is 1 joule per second
The space shuttle uses MW of power in 20 seconds

15. What are the two forms of mechanical energy?
Hint one form has to do with the position of something and the other has to do with the motion of something .
Kinetic energy Potential Energy

16. Do you know what all of these have in common?
Rubber bands
Gasoline
Objects on a cliff
These are all examples of potential energy.
Elastic
Chemical
Gravitational

17. Gravitational Potential Energy
Is equal to the work done to lift the object to that height
GPE = mgh
= mass gravity height

18. Kinetic Energy
KE = 1/2mv2
Is equal to the work required to bring an object to speed from rest of bring a moving object to rest
Fd = 1/2mv2

19. Work –Energy Theorem Whenever work is done energy changes.
Work = change in kinetic energy

20. The Law of Conservation of Energy
Energy cannot be created or destroyed but can transform from one form to another, but the total energy never changes.
Where is the highest kinetic energy on a pendulum?
The lowest kinetic energy?
What is type of energy is KE changing to and from on its path?