Forms of Energy

Bell work and Agenda 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.

Bell work Day 4 -- answers 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. Answer: When you throw a ball up in the air. 4. What is the unit for energy? Answer: joules

Q: Why is density useful for identifying elements? 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: Why 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. SC8.2.1.g DOK 2

Q: What is the most dense solid shown on the table? mercury pyrite silver zinc SC8.2.1.g DOK 2

A: What is the most dense solid shown on the table? A. mercury 13.55 g/cm3 is the most dense liquid, not solid. B. pyrite 5.02 g/cm3 is not the most dense solid. C. silver 10.50 g/cm3 is the most dense solid. D. zinc 7.13 g/cm3 is not the most dense solid. SC8.2.1.g DOK 2

MATH BOOSTER Day 4 A shop owner increased the selling price of a shirt from $20 to $27. By what percentage was the price increased?

MATH BOOSTER Day 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 %

Greek and Latin Day 4 Greek /Latin Picture dynam- -erg- grav- kilo-   -erg- grav- kilo- kine-

Objective Day 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 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. 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.

Forms of Energy What are the major forms of energy? Have a class discussion on the major forms of energy.

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 Have a class discussion to see if students have any ideas of the major forms of energy.

Gizmo Exploration Energy Conversions Gizmo Complete packet Show Mrs. Vaughan Take quiz

Forms of Energy 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

Forms of Energy 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.

Forms of Energy Electrical Energy Electrical energy is the energy associated with electric charges.

Chemical Energy: The energy stored in chemical bonds.

Forms of Energy 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.

Forms of Energy Nuclear Energy The energy stored in atomic nuclei is known as nuclear energy.

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

Energy Conversion -- examples 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. NO NOTES. These examples are to help students understand. Make sure to talk about them.

A tells B: Explain why speed skaters are slowed down, even though they slide quickly over smooth ice. There is music with this slide.

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

Energy Conversions – PE to KE The gravitational potential energy of an object is converted to the kinetic energy of motion as the object falls.

Energy Conversion -- examples 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. Don’t have the students take these as notes. Just discuss these examples and you can also ask for more!

Fun Fact: 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. Don’t have students put these in their notes. Just discuss this as a group.

Energy Conversion in Pendulums A pendulum consists of a weight swinging back and forth from a rope or string. If students know what a pendulum is, they do not need to write that in their notes.

At this point the energy of position is full, so it has PE!

While it is moving it has kinetic energy, but it also has energy of position.

There is no longer any PE but there is KE!

Finally, there is no movement so there is only energy of position.

The TOTAL amount of energy is conserved!

As the pendulum swings downward, PE is converted to KE. 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. Students should not have to write down in their notes what pole vaulting is, but do have students take notes over the pole vault material on the next slide. There is a question on the test over it.

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.

Mechanical Energy (total energy) Equation: Mechanical energy =KE +PE When friction is small enough to be ignored, and no mechanical energy is added to a system, then the system’s mechanical energy does not change. There is sound with this file.

ME = 10 J NO KE = 0 J MOVEMENT WHY? PE = 10 J Group practice KE = ? ME = ? NO MOVEMENT KE = 0 J WHY? ME = 10 J Explain that a ball sits on the shelf and its PE is 10 J. What is its KE at the top of the shelf? It is zero because there is no movement. Ask what the ME (total energy) is at the top of the shelf.

ME = ? ME = 10 J ½ way down KE = ? PE = ? KE = 5 J PE = 5 J Now explain that someone comes along and hits the ball off the shelf. ½ way down what would the KE be? PE? ME?

Nanosecond before it hits the ground KE = ? PE = ? KE = 10 J PE = 0 Nanosecond before it hits the ground KE = ? PE = ? ME = ? ME = 10 J The reason “nanosecond before it hits the ground” is there is so students do not get confused with when it hits the ground it will stop and there will be no PE or KE. Nano means billionth

Rally Coach (B tells A what to write) 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/s2)(3 m) PE = 58.8 J (We know that the KE & PE are switched. ) Therefore, KE = 58.8 J

Physical Science Text Book Homework Physical Science Text Book 1. Read pages 450 – 457 2. Answer Questions #1 – 22 on page 469