1. Do Now:
Use the seating chart below to find your new seat. Once you’ve sat down, begin working on the following questions:
What does the word “energy” mean to you?
What types of energy do you think exist in the universe?

2. Work and Energy
New Unit! 1/26/22

3. Extra Credit Opportunity:
Hold an individual conference with me outside of class
Worth two homework grades of extra credit
If you are interested pick up a pre-conference form from me and sign up for a ten minute slot on my door

4. New Unit: Work and Energy
Energy:the capacity of a physical system to change or perform work.
All energy is either potential or kinetic:
Potential: stored
Kinetic: energy of motion

5. Types of Energy:
Mechanical: The energy acquired by the objects upon which work is done; can be kinetic or potential
Ex: moving water; a rolling object

6. Types of Energy:
Chemical: The energy stored by chemical reactions; potential
Ex: food, batteries

7. Types of Energy:
Thermal: created by heat. The hotter an object becomes the more thermal energy it possesses.

8. Types of Energy:
Electromagnetic: energy produced when something upsets the balancing force between electrons and protons in atoms; can be kinetic or potential

9. Types of Energy:
Nuclear: energy locked in the nucleus of the atom. Nuclear power plants split atoms in a process called fission

10. Types of Energy:
Solar: energy from the sun

11. Types of Energy:
Radiant (Light): waves that emit energy. Examples include: radio and television waves, gamma rays, and x- rays and sound

12. Types of Energy:
Gravitational Energy - energy stored as a result of gravitational forces concentrated by the earth for the object. Water held back by a dam is an example of gravitational energy.

13. Practice:
Work in groups to identify the types of energy in each example. There may be more than one in each!

14. Do Now: Determine the types of energy in the following examples:
Playing a PSP
Lighting a match
Shoveling snow
Skydiving
Using wind to create electricity

15. W=Fd Measured in Nm or joules (j) Work
Work: a force exerted over a distance
W=Fd
Measured in Nm or joules (j)

16. Determine if work is done:
A person pushing a wheelbarrow 5 m
A person pushing a wall that doesn’t move
A car traveling from Baltimore to New York
A book sitting on a table
Something being dropped from 15 m
A car moving at constant speed for 10 miles

17. Kinetic Energy:
KE= ½ mv2
Measured in joules (j)

18. The Work-Energy Theorem
W=∆KE
Fd= ½ mvf2 - ½ mvi2
W= ½ mvf2 - ½ mvi2
Fd=∆KE

19. Practice:
Use the rest of class to work on the worksheet

20. Do Now:
A force of 15 N is required to push an object a distance of 3 m.
What is the work done?
What is the change in kinetic energy?
A 20 kg dog can run at 15 m/s. What is its kinetic energy?

21. PE=mgh Potential Energy
Potential energy: energy stored within a system; can be converted into kinetic energy; represented by either PE or U
Gravitational Potential Energy:
PE=mgh
Where:
m=mass
g=acceleration due to gravity ( on earth -9.8 m/s2)
h=height or distance from the reference level
Reference level: the position where the PE is determined to be zero

22. Example:
Determine the potential energy of a 2 kg ball on a cliff if the cliff rises 50 m above the ground.

23. Example:
Determine the potential energy of the same 2 kg ball once it drops to 20 m.

24. Power Rate of change of work or energy of a system:
Power=work/time; measured in Watts (W)
1 W = 1 j/s

25. Example:
100 j of work are exerted for 12 s. What is the power?

26. You will have a quiz on energy on Tuesday, 2/8!!!
Practice:
Use the rest of class to work on the worksheet: Power and Potential Energy
You will have a quiz on energy on Tuesday, 2/8!!!