unit 4 notes

States that energy cannot be created nor destroyed, it can only be changed (transferred).

• energy can be transferred to another object/system or into another form

  • example:

    • a roller coaster

      • at the top of the coaster you have potential energy but when you drop it turns to kinetic energy

Law of Conservation of Energy

Unit4

Multiple Choice

The Law of Conservation of Energy states:

• Energy can created or destroyed but not transformed 

• Energy cannot be created or destroyed, it can only transformed

• Energy can't be created, destroyed or transformed

I know...

• how to identify the type of energy when presented with an image.

Learning Target

I can...

• ​construct explanations for energy transformations within a system.

​​Success Criteria

Whenever work is done, energy is transformed or transferred to another system.

• Energy is the ability to do work.​

Energy and Work

Energy and Work

Misconception:

• only things that are moving have energy.

  • Energy can be present in an object or a system when no​thing is happening.

  • Once an object moves in the direction of the force being applied, we can observe work being done as energy is transferred ​from one object to another

Types of Energy

​Mechanical	​Potential	Kinetic
Chemical	Thermal	Nuclear
Electrical	​Electromagnetic	Sound

​Each of these forms of energy can be converted into other forms of energy.

definition: the energy associated with the motion or position of an object.

• this is the sum (total amount) of potential and kinetic energy in a system.

  • Kinetic energy: the energy of motion

  • Potential Energy: the energy that is stored in an object (energy of position)

Mechanical Energy

definition: the energy stored in chemical bonds

• when bonds are broken the released energy can do work​

Chemical Energy

definition: energy that results from the flow of electrons

• electric charges can exert forces that do work​

Electrical Energy

definition: the energy stored in atomic nuclei

• Remember:

  • nuclear fission releases energy by splitting nuclei apart

  • nuclear fusion combines 2 nuclei into a larger nucleus​ which releases energy

Nuclear Energy

definition: energy that moves through a substance such as air or water

• this is caused by vibrations (periodic back-and-forth motion).

• Solids, liquids and gases can transmit sounds as waves.

​

Sound Energy

definition: energy given off as heat (friction)

• Force vs Friction

  • Friction is a type of force that opposes motion, or makes it difficult for an object to move across a surface.​

​

Thermal Energy

definition: energy that travels through space in the form of waves (also called radiant energy)

• visible light and x-rays are examples of electromagnetic energy​

Electromagnetic Energy

This is the process of changing energy from one form to another

Energy Conversions

​Chemical

Energy​

​Mechanical

Energy​

​Kinetic

Energy​

​Label Roller Coaster

This interactive roller coaster ride produced by WGBH illustrates the relationship between potential and kinetic energy.

Click the button that says "STEPS" and record what happens a points A-F

https://contrib.pbslearningmedia.org/WGBH/conv16/conv16-int-rollercoaster/index.html

Multiple Choice

Which specific type of energy is at point B?

• Potential Energy

• Kinetic Energy

• Mechanical Energy

• None

Multiple Choice

During which point is potential energy the highest?

• W

• X

• Y

• Z

Multiple Choice

During which point is kinetic energy the highest?

• W

• X

• Y

• Z

Energy Transformation Practice

Energy Transformations can be multi-stepped.

Ex: Hairdryer

Electrical (plugging it in) --> Mechanical (spinning of the fan)--> Heat (hot air)

Let's look at a flashlight

• It runs on batteries (chemical energy)

• When it turns on, it's changed from chemical into electrical

• Then, it is transformed into light energy.

What type of energy transfer is being shown?

What type of energy transfer is being shown?

​Chemical

​Mechanical (movement)

Multiple Choice

What type of energy transformation is being shown in the image?

(eaten apple --> person riding a bike)

• chemical to light

• electrical to light

• chemical to mechanical

• light to heat (thermal)

Multiple Choice

What type of energy transformation is being shown in the image?

(battery --> flashlight)

• chemical to light

• potential to light

• chemical to mechanical

• light to heat (thermal)

Multiple Choice

What type of energy transformation is being shown in the image?

(sun --> tree)

• chemical to light

• electrical to light

• radiant to chemical

• light to heat (thermal)

Multiple Choice

What type of energy transformation is being shown in the image?

(plug --> lamp)

• chemical to light

• electrical to light

• radiant to chemical

• light to heat (thermal)

Multiple Choice

Atomic bomb's energy transformation:

_______ --> kinetic, _______ and __________

• nuclear, sound, and thermal

• sound, light, and nuclear

• nuclear, chemical, light

• chemical, thermal, and sound

Multiple Choice

A tree's energy transformation is:

_______ --> _________

• light and sound

• light and chemical

• nuclear and sound

• nuclear and chemical

Multiple Choice

Playing musical instruments:

____________ --> _________

• sound and light

• chemical and radiant

• kinetic and sound

• kinetic and thermal

Multiple Choice

Food's energy transformation is:

________ --> thermal, _________

• chemical and kinetic

• chemical and radiant

• thermal and radiant

• sound and chemical

Quick recap: what are the 7 main forms of energy?

• Chemical

• ​Sound

• Electrical

• Radiant/Light

• Mechanical

• Thermal

• Nuclear

Some helpful hints

• If you have to plug it in ........ conversions likely starts with electricity

• If it is battery powered..... first 2 steps are chemical --> electrical

• If it produces electricity......... last step is likely electrical

​Extra Practice

https://isaacphysics.org/questions/kinetic_energy_quiz_a?stage=all

Multiple Choice

Which of the following best describes the thermal energy of a material?

• The ability of the material to allow heat to pass through it

• The heat the material absorbs, minus the heat it releases

• The total kinetic energy of all of the particles in the material

• The energy needed to change the state of the material

Calculating Kinetic & Potential Energy

​KE is the kinetic energy (in joules),
m is the mass of the object (in kilograms),
and v is the velocity of the object (in meters per second).

In this case, the mass (m) is 4 kg, and the velocity (v) is 8 m/s.
Plugging these values into the formula:
KE = 0.5 * 4 kg * (8 m/s)^2
KE = 0.5 * 4 kg * 64 m^2/s^2
KE = 128 joules
So, the kinetic energy of the 4 kg rock moving at 8 m/s is 128 joules.

​How much kinetic energy is in 4 kg rock moving at 8 m/s?

​in this case, the mass (m) is 10 kg, and the velocity (v) is 20 m/s. Plug these values into the formula:
KE = 0.5 * 10 kg * (20 m/s)^2
KE = 0.5 * 10 kg * 400 m^2/s^2
KE = 2000 joules
So, the kinetic energy of the 10 kg rock thrown at 20 meters per second is 2000 joules.

​How much KE is in a 10 kg rock that is thrown at a rate of 20 meters per second?

Formula-KE = ½ mv2

Multiple Select

Kinetic energy depends on the ________ and ________ of the object.

• Height (position)

• Mass

• Speed

• Friction

Multiple Choice

If the Total Mechanical Energy is 50J, Potential Energy is 40 J, what is the Kinetic Energy?

• 1 J

• 10 J

• 90 J

Multiple Choice

The equation KE = 1⁄2 mass x velocity² is used to find which type of energy?

• Kinetic Energy

• Potential Energy

Multiple Choice

The faster an object moves, the ________ kinetic energy it has.

• more

• less

Multiple Choice

A car is traveling with a velocity of 20 m/s and has a weight (mass) of 1000 kg. Calculate how much kinetic energy the car has.

• 200,000 J

• 100,000 J

• 400,000 J

Multiple Choice

A baby carriage is sitting at the top of a hill that is 20 m high.

The carriage with the baby in it weighs 40 kg.

What type of energy does this baby carriage have?

• kinetic

• potential

Multiple Choice

What is the kinetic energy of a ball with a mass of 5kg rolling at 10m/s

• 50 J
• 5 J
• 250 J
• 25 J

Multiple Choice

A baby carriage is sitting at the top of a hill that is 20 m high.

The carriage with the baby in it weighs 40 kg.

Calculate how much potential energy the carriage with baby has?

• 800 J

• 8000 J

• 80 J

​In this case, the mass (m) is 10 kg, and the height (h) is 50 meters above the ground.
Using the formula: GPE = 10 kg * 9.81 m/s^2 * 50 m
GPE = 4905 joules
So, the gravitational potential energy of the 10 kg rock 50 meters above the ground is 4905 joules.

​How much GPE is in a 10 kg rock that is 50 meters above ground?

Formular GPE= (m)(h)(a)

Heat Transfer

Multiple Choice

The equation PE = mass x gravity x height is used to find which type of energy?

• Kinetic Energy

• Potential Energy

What type of energy is temp.?

Energy Transfer

I know…

• how to define conduction, convection, and radiation.

​​Learning Target

I can…

• describe how molecular motion relates to thermal energy.

Success Criteria

Multiple Choice

A 1.5 kg football is thrown with a velocity of 15 m/s. What is the kinetic energy of the football?

• 168.75 J

• 22.5 J

• 10 J

• 220.5 J

definition: the measure of the average kinetic energy in an object.

• particles within a substance are constantly moving (kinetic energy)

• as temperature increases, kinetic energy will also increase​

​​What is temperature?

• 3 units

  • Celsius (^oC)

  • Fahrenheit (^oF)​

    • American scale

    • rarely used in science​

  • Kelvin (K)​

    • 0 K is absolute zero = -273.13 ^oC​

Measuring Temperature

​Heat is transferred only when two objects are at different temperatures

• Thermal energy always moves from warmer to cooler objects

• The warmer object loses thermal energy and becomes cooler 

• The cooler object gains thermal energy and becomes warmer.

• Energy will continue to move from a warmer object to a cooler object until both have the same temperature.

• What type of energy is temp.?

  • temperature is energy transferred as heat (thermal energy)

  • energy must move for heat to occur​

• What is heat?

  • definition: the transfer of energy between the particles of 2 objects due to a difference in temperature​

Energy Transfer

• heat flows from high temperature to low temperature.

• What happens to your feet once you place it in front of a heater?

  • Answer: the warmth (heat energy) moves from the heater (high temp) to your cold feet (low temp)

How does heat flow?

There are 3 types of heat (thermal) energy transfers

1. Conduction

2. Convection

3. Radiation​

What is Conduction?

definition: heat (thermal) transfer of energy by direct contact

• the 2 objects in contact are at unequal temperatures.

• the heat will move from the warmer object to the colder object​

• Examples

  • holding a hot cup of hot chocolate with cold hands​, the heat from the cup will be transferred directly to your hands

  • ​ironing clothes, the iron is hot and by touching the clothes the heat is transferred directly to the clothing.

What is Convection?

definition: heat transfer of energy by the movement of a heated fluid/medium— this includes a liquid or a gas.

• heat transfer happens because there density changes as the fluid begins to warm.

• the phrase "hot air rises​" is correct because gases expand and rise as they heat up and become less dense than cold gas particles

What is Convection?

• Examples:

  • ​a space heater, it puts out warm air from the top and draws in cooler air at the bottom to heat up a room (air/gas is the medium)

  • boiling water, the cold water at the bottom gets warmer and rises because of the energy in the burner and then the cold water rushes down to replace it at the bottom.

What is Radiation?

definition: heat that gets transferred in rays/waves from one place to another WITHOUT any physical contact or a medium

• transfer of energy happens through electromagnetic waves (infrared, visible light, ultraviolet)​

• does NOT require the movement of matter

What is Radiation?

• Example

  • standing in sunlight​; radiation from the sun is a mixture of electromagnetic waves

    • most of the radiation is absorbed by the atmosphere, but people are exposed to the rest

Multiple Choice

Which of the following is an example of convection?

• sitting under a lamp at your desk

• a car engine getting hot after you turn the car on

• water boiling when cooking noodles on the stove

• your feet getting warm from the hot sand on the beach

Multiple Choice

The heat moving from a hot burner to a pot that is sitting on the stove is an example of which heat transfer?

• conduction

• absorption

• radiation

• convection

Multiple Choice

To keep the baby chickens warm a farmer uses heat lamps, this is an example of ______.

• conduction

• convection

• radiation

• isolation