1. CONSERVATION OF ENERGY
KINETIC POTENTIAL
MECHANICAL

2. ENERGY the ability to change or move matter
Law of Conservation of Energy: energy cannot be created or destroyed! (It can only change form!)
electrical heat + light

3. KINETIC ENERGY . . . IS MOVEMENT!
Examples:
Of electrons: ELECTRICAL ENERGY
Of electromagnetic waves:
RADIANT ENERGY (x-rays, UV,
radio waves, microwaves, etc.)
Of heat: THERMAL ENERGY
Of a moving object:
MECHANICAL ENERGY

4. CALCULATING KE: KE = mv2 mass = kg 2 velocity = m/s KE = Joules (J)
EQUATION: UNITS:
KE = mv mass = kg
2 velocity = m/s
KE = Joules (J)
On your formula chart you will see this as :
Kinetic Energy = ½ (mass × velocity2)

5. SAMPLE PROBLEM:
What is the [kinetic energy] of a 44 kg cheetah running at 31 m/s?
G m = 44 kg, v = 31 m/s
U KE = ?
E KE = (mv2)/2
S KE = (44 kg)(312 m2/s2)/2
S KE = 21,142 J

6. POTENTIAL ENERGY . . . IS STORED OR POSITIONAL!
Examples:
In batteries: ELECTRICAL ENERGY
In bonds: CHEMICAL ENERGY
(fossil fuels, glucose)
In an atom’s nucleus:
NUCLEAR ENERGY
In machines: ELASTIC ENERGY (springs, rubber bands)
Of position (height): GRAVITATIONAL

7. CALCULATING GPE: (Gravitational Potential Energy)
Your Formula Chart shows the formula for GPE as:
Gravitational potential energy = mass x acceleration due to gravity x height
EQUATION: UNITS:
GPE = mgh mass = kg
acceleration due to gravity = g = 9.8 m/s2
height = m
Weight = mg Weight = Newtons
GPE = Joules

8. SAMPLE PROBLEM: G m = 2.0 kg, h = 12 m U GPE = ? E GPE = mgh
What is the GPE of a 2.0 kg rock that sits on the edge of a cliff 12 m high?
G m = 2.0 kg, h = 12 m
U GPE = ?
E GPE = mgh
S GPE = (2.0 kg)(9.8 m/s2)(12 m)
S GPE = J

9. MECHANICAL ENERGY Equals the TOTAL energy in a system!
Is the sum of the PE and the KE.
ME = KE + PE
Gradually decreases
because of friction
(lost as heat).

10. Mechanical Energy in a Swinging Pendulum
1. At which point(s) is KE greatest? Why?
2. At which point(s) is PE greatest? Why?
MAX PE
MAX PE
MAX KE
1. #3; the faster it moves, the greater its KE.
2. #1, #5; the higher it is, the greater its PE.

11. If there is no loss of energy due to friction, the total (mechanical) energy remains the same!
The KE and PE of a roller coaster changes as it travels down the track, depending on its speed and height.

12. Quiz
Directions: Identify the type of energy described in each problem below. Do not solve the problem.
A box on the shelf 2 meters high with a mass of 20 kg.
A ball rolling along a shelf that has a velocity of 5 m/s and a mass of 100 g.
A marble with a mass of 15 g at the top of a 15 cm tall slope.
A weight bar and weights that have a mass of 250 kg lifted up to a height of 2.5 m.
An automobile with a mass of 2000 kg and a velocity of 50 m/s. 12

13. Quiz (KEY)
Directions: Identify the type of energy described in each problem below. Do not solve the problem.
A box on the shelf 2 meters high with a mass of 20 kg. Potential energy
A ball rolling along a shelf that has a velocity of 5 m/s and a mass of 100 g. Kinetic energy
A marble with a mass of 15 g at the top of a 15 cm tall slope. Potential energy
A weight bar and weights that have a mass of 250 kg lifted up to a height of 2.5 m. Potential energy
An automobile with a mass of 2000 kg and a velocity of 50 m/s. Kinetic energy 13

14. Forms of Energy and Energy Transformation
Part 2
Forms of Energy and Energy Transformation

15. Forms of Energy Six forms of energy are: Mechanical Energy Heat Energy
Electromagnetic Energy
Chemical Energy
Radiant Energy
Nuclear Energy 15

16. Energy Transformation
Energy is always changing from one form to another.
The Sun, primary source of energy on the Earth.
Nearly all energy comes from the sun.
Energy cannot be created or destroyed. (AKA: Law of Conservation of Energy) 16

17. The Flow of Energy
The Sun,
Nuclear
Energy
The Sun gives off Radiant energy in the form of light
Earth
Energy received by the Earth is converted into heat and chemical energy. 17

18. The Flow of Energy
Plants convert light (radiant energy) into chemical energy (sugar or glucose) through a process called Photosynthesis.
When light from the Sun hits the Earth the radiant energy is transformed into heat energy. 18

19. Energy Transformation
There are many examples of energy transformations. Give an example for each arrow in the following diagram.
Electromagnetic
Radiant
Nuclear
Mechanical
Heat
Chemical 19

20. Energy 20