1. Give an example in which one form of energy changes to another form of energy.
2. Give an example in which PE changes to KE.
3. Give an example in which KE changes to PE.
4. What is the unit for energy?
Agenda
Energy Conservation Gizmo
Notes over different forms of energy.
Discuss the Law of Conservation of Energy.

1. Give an example in which one form of energy changes to another form of energy.
Answer: A light bulb, in which the electrical energy changes to light energy or sound energy or both.
2. Give an example in which potential energy changes to kinetic energy.
Answer: A marker falling off a desk.
3. Give an example in which kinetic energy changes to potential energy.
A nswer: When you throw a ball up in the air.
4. What is the unit for energy?
Answer: joules

Q: W HY IS DENSITY USEFUL FOR
IDENTIFYING ELEMENTS ?
A.
B.
C.
D.
Density predicts whether objects float.
Density varies at different temperatures.
Density is often unique to each element.
Different elements have the same densities.
SC8.2.1.g DOK 2

A: W HY IS DENSITY USEFUL FOR
IDENTIFYING ELEMENTS ?
A. Density predicts whether objects float.
Objects of various densities will float, but do not identify elements.
B. Density varies at different temperatures.
Density does not vary with temperature.
C. Density is often unique to each element.
Different elements tend to have different densities.
D. Different elements have the same densities.
Different elements tend to have different densities.
SC8.2.1.g DOK 2

Q: W HAT IS THE MOST DENSE SOLID
SHOWN ON THE TABLE ?
A.
mercury
B.
pyrite
C.
silver
D.
zinc
SC8.2.1.g DOK 2

A: W HAT IS THE MOST DENSE SOLID
SHOWN ON THE TABLE ?
A. mercury
13.55 g/cm 3 is the most dense liquid, not solid.
B. pyrite
5.02 g/cm 3 is not the most dense solid.
C. silver
10.50 g/cm 3 is the most dense solid.
D. zinc
7.13 g/cm 3 is not the most dense solid.
SC8.2.1.g DOK 2

MATH BOOSTER D AY 4

MATH BOOSTER D AY 4 -ANSWER
A shop owner increased the selling price of a shirt from
$20 to $27. By what percentage was the price increased?
Increase in the price = $27 - $20 = $7
Percentage increase in the price = × 100
= (7 ÷ 20) × 100
= 35 %

G REEK AND L ATIN D AY 4
Greek /Latin Picture dynam-
-erggravkilokine-

O BJECTIVE D AY 4
1. I will know the different forms of energy and the law of conservation of energy.
2. I will be able to apply the law of conservation of energy.

Energy classifications:
1. kinetic energy
2. potential energy
3. energy in fields such as those produced by electromagnetic waves
Each of these forms of energy can be converted into other forms of energy.


What are the major forms of energy?


What are the major forms of energy?

The major forms of energy are: mechanical energy thermal energy chemical energy electrical energy electromagnetic energy nuclear energy

G IZMO E XPLORATION

Energy Conversions Gizmo



Complete packet
Show Mrs. Vaughan
Take quiz

Mechanical Energy




The energy associated with the motion and position of everyday objects is mechanical energy.
Mechanical energy is the sum of an object’s potential energy and kinetic energy.
What does sum mean?
ADDITION

Thermal Energy

The total potential energy and kinetic energy of all the microscopic particles in an object make up its thermal energy.

When an object’s atoms move faster, its thermal energy increases, and the object becomes warmer.

Electrical Energy

Electrical energy is the energy associated with electric charges.

C HEMICAL E NERGY :

Electromagnetic Energy

Electromagnetic energy is a form of energy that travels through space in the form of waves.
Visible light and X-rays are examples of electromagnetic energy.

The Law of Conservation of
Energy states that energy cannot be created or destroyed, it can only change form.


The work done by friction changes kinetic energy into thermal energy.
• Friction within machinery reduces efficiency. Friction is a major cause of energy consumption in cars and factories.
• In many cases, most of a falling object’s potential energy is converted into thermal energy because of air resistance.


Explain why speed skaters are slowed down, even though they slide quickly over smooth ice.


They are slowed down by friction with the air and the surface of the ice.



• An avalanche brings tons of snow from the top of a mountain to the valley floor.
• The elastic potential energy of a compressed spring is converted into kinetic energy as the spring expands.


Some gulls use energy conversion to obtain food by dropping oysters onto rocks. Kinetic energy causes the shell to break on collision with the rock.

Energy Conversion in Pendulums
A pendulum consists of a weight swinging back and forth from a rope or string.

A
,
PE!

W HILE IT IS MOVING IT HAS
KINETIC ENERGY , BUT IT ALSO
HAS ENERGY OF POSITION .

T
PE
KE!

F
,
.

T
!

Summary:
Energy Conversion in Pendulums
• At the highest point in its swing, the pendulum has zero KE and maximum PE.
•
•
As the pendulum swings downward, PE is converted to KE.
At the bottom of the swing, the pendulum has maximum
KE and zero PE.

Energy Conversion and the Pole Vault
In the pole vault, an athlete uses a flexible pole to propel it over a high bar.

1. Some of the pole-vaulter’s kinetic energy is converted into elastic potential energy as the pole bends.
2. The pole springs back into shape, propelling the pole-vaulter upward.
3. As the pole-vaulter rises, the kinetic energy decreases while the gravitational potential energy increases.
4. Once the highest point has been reached, the gravitational potential energy begins to convert back to kinetic energy.

PE = 10 J G ROUP PRACTICE
KE = ?
ME = ?
KE = 0 J
WHY?
ME = 10 J

½ WAY DOWN
KE = ?
PE = ?
KE = 5 J
PE = 5 J
ME = ?
ME = 10 J

N
KE = ?
PE = ?
KE = 10 J
PE = 0
ME = ?
ME = 10 J

1. A 2 kg heavy ball falls from a 3 m shelf. Just before hitting the floor, what is its kinetic energy?

Answer : According to the Law of
Conservation of Energy, total energy at the top will be equal to the total energy at the bottom.


Total energy at top = Total energy at bottom
PE = mgh

= (2 kg)(9.8 m/s 2 )(3 m)
PE = 58.8 J
(We know that the KE & PE are switched. )
Therefore,
KE = 58.8 J

1. Read pages 450 – 457
2. Answer Questions #1 – 22 on page 469