1. Unit 3: Work, Energy, and Power

2. Conservation of Energy!!

3. Energy as a tool in physics
Energy is a very abstract notion, but it is a very useful and quantifiable notion
We use the law of conservation of energy to predict behavior
We rely on the fact that energy is not created out of nowhere
Where did the energy we see around us come from?
most of what we use derives from the sun
some derives from other, exploded stars (nuclear fission)
ultimately, all of it was donated in the Big Bang!

4. Energy cannot be created or destroyed
It's the LAW!
Of conservation of energy
Energy cannot be created or destroyed

5. All energy can be broken down into 2 categories
Types of Energy
All energy can be broken down into 2 categories
Energy!
Kinetic Energy
Potential Energy

6. K=½ mv2 Kinetic energy Energy! An objects kinetic energy is equal to……
Which has a bigger affect????
kinetic energy = energy due to motion

7. If this car had a velocity of 24 m/s and a mass of 1000 kg what was its kinetic energy when it entered your living room?
joules
15000 joules
49000 joules
joules

8. Ug = mgh gravitational Potential Energy Energy!
An objects Gravitational Potential energy is equal to……
Energy!
Ug = mgh
Which has a bigger affect????
Potential energy = stored energy in earth
1644 m staircase

9. Calculate Spidey’s gravitational potential energy if he is 150 m up a building and his mass is 89 kg!!!
joules
4388 joules
joules
94224 joules

10. An objects Thermal energy is equal to……
Dissipated Energy
An objects Thermal energy is equal to……
This is energy that is hard to reclaim from the system. Even though the energy is not lost, it is hard to convert into another form of energy.
Energy!
An object gives off thermal energy in the form of heat! This is where %75 of your energy goes!!
kinetic energy = energy due to motion of molecules, but it is extreme hard to reclaim

11. Elastic and spring Potential Energy Energy!
An objects elastic potential is equal to……
Relax! Right now you need to understand that it is another form of potential energy!
Energy!
Think bow and arrow, rubber bands, springs, catapults, sling shots, etc.
Potential energy = stored energy in the spring

12. Mechanical vs. Non-mechanical energy
Mechanical energy – Potential and Kinetic Energy
The total mechanical energy of a system will be the sum of the potential and kinetic energy
Energy!
Non-Mechanical energy – everything else! Light, Sound, Chemical, thermal.

13. It's the LAW! Remember! Energy cannot be created or destroyed!!
Of conservation of energy
Energy cannot be created or destroyed!!
So what happens to an object’s potential and kinetic energy as it moves?!?
The point is: Energy is never lost… just transferred!
So does an object lose or gain energy as it moves?!?

14. Doing “Work” on objects
Work in physics is when energy is transferred into, out of, with in the system.
Work in the system can result in a change in Kinetic Energy OR a change in Potential Energy.
Can be positive (net gain in energy) or negative (net loss in energy)
Work is accomplished by applying a FORCE through a DISTANCE.
Work = Force x distance
W = Fd
Anytime there is a change in energy, you do work!

15. Lets say this fat kid pulls his wagon with a force of 300 N
Lets say this fat kid pulls his wagon with a force of 300 N. How much work does he do on wagon if he pulls it for a distance of 35 meters?
8.57 joules
7,777 joules
4,322 joules
10,500 joules
W = Fd

16. Units Work & Energy are scalar quantities.
Joule (J) – SI unit for Work & Energy
James Prescott Joule ( ) – English physicist; studied heat and work.
This led to the theory of conservation of energy. Developed Kelvin scale with Lord Kelvin.