1. November 23, 2015 Work and Power Quiz moved to Dec. 1
University of Texas Assignment Due TODAY.
No new University of Texas Assignment this week, next one will be opened on November 30th.

2. Goals To explain different types of energy
To calculate potential and kinetic energy
Eureka Kinetic Energy
Eureka Potential Energy

3. Q: What is ENERGY? Energy is…. the ability to do work
a measure of how much work is done
a word to describe the power and effort of a force.
measured in Joules

4. ENERGY Energy is the ability to do work Doing work uses energy
An object can gain energy if work is done on it

5. Q: What is ENERGY? Two MAIN types of mechanical energy:
Potential energy
Kinetic Energy

6. Q: What is POTENTIAL ENERGY?
Potential Energy (PE) is stored energy
Coaster has PE when it is at the top of the hill. Even if it isn’t moving yet, it may if a force is applied and it begins to move

7. Q: What is POTENTIAL ENERGY?
Gravitational potential energy (GPE) is the energy of an object due to its position above the surface
GPE = mgh = wh
m=mass (in Kg)
g=acceleration due to gravity … 9.8 m/s2
h= height (in m)
w = weight (N)
UNITS: kg x (m/s2) x m = N-m = Joule (J)

8. Practice Problem PE PE m g w h h

9. PRACTICE PROBLEM: Find the PE of a rock climber as she climbs 35 m above the base of a cliff. Her mass is 65 kg.
Equation:
GPE = mgh
Given:
h = 35 m
m = 65 kg
g = 9.8 m/s2
GPE = ?
Solve: GPE =
65 kg x 9.8 m/s2 x 35m
=22,295 J

10. Q: What is KINETIC ENERGY?
Kinetic Energy (KE) is the energy due to an object’s motion
Active energy
A rock as it falls off of a cliff
Formula: KE = ½ * m * v2
m= mass (kg)
v = velocity (m/s)
UNITS: kg X (m/s)2 = Joule (J)

11. PRACTICE PROBLEM: What is the KE of a 44 kg Cheetah running at 31 m/s?
Given:
m = 44 kg
v = 31 m/s
KE = ?
Equation:
KE = ½ * m * v2
Solve: KE =
(1/2) (44 kg) (31 m/s)2
21,142 J

12. Q: What is the Law of Conservation of Energy
This is similar to the Law of Conservation of Mass/Matter!
The Law of Conservation of Energy says energy cannot be created or destroyed, but it can be transformed from one form to another.

13. Forms of energy: Mechanical (Motion-PE and KE, includes sound)
Heat (friction)
Electromagnetic (includes light and electricity)
Chemical
Nuclear

14. Energy Transformation
Energy Transfer
Energy moves from one object to another
ex. Boiling water on stove
Energy Transformation
Energy changes from one form to another
Ex. Light  heat

15. Examples of Energy Transformations:
Ex) On a roller coaster ride all of the energy for the entire ride comes from the conveyer belt at the beginning of the ride.
This energy is then stored as GPE at the top of the first hill.
As the coaster travels down the first hill, the GPE is converted to KE.
In the real world, a small amount of this energy is lost as heat to the wheels and vibrations that produce the roaring sound!

16. KE + PE = Total Energy
At the top of a hill, KE = 0 J. All energy is PE.
At the bottom, all the energy that was PE at the beginning has been changed into KE. (so now PE = 0 and all energy is KE)

17. Homework Continue working on lab packet-Friday’s Lab
Finish Homework Packet 1