Energy

SPS7a: Identify energy transformations within a system.

Essential Question:What is energy and what are

the different forms?

Energy :

the ability to do work

• Examples of energy are all around you.

• Energy is connected to work.

• Energy is measured in the same unit as work, joules (J).

We are more used to the unit of energy called the calorie. 1000 calories = 1 kilocalorie, which is written as Calorie. A 100 Calorie cookie has 100 kilocalories of energy.

__________ Potential Energy

Potential Energy, PE:The energy of position. Examples: spring, stretched rubber band, any object that could fall.

Gravitational Energy of an object

because of its height.Example: waterfall

Stored energy

Potential Energy

• It has the ability or potential to give that energy back by doing work.

• Potential energy does not always have to be mechanical energy.

• Example: energy stored in food. This energy is chemical. The energy is stored in the food and released when the food is broken down through digestion

3 m -> had more PE

Which hurts more, a bowling ball dropped on your foot from a height of .10 m or from 3 m?

Kinetic Energy, KE: Energy of motion

•The faster an object moves the more kinetic energy it has.

•Kinetic energy is directly related to the velocity of an object

•Kinetic energy depends on both mass and velocity.

Which hurts more when dropped on your foot, a ping pong ball or a bowling ball at 5 m/s?Bowling ball – more mass –

more energya tennis ball at 2m/s or 20 m/s?20 m/s – more speed –

more energy

Find all the PE stored in this situation.

The Law of Conservation of Energy

Which means energy is notCreated or

destroyedEnergy can be transferred from one object to another and can be changed from one form to another.

ENERGY IS CONSERVED!!

Roller coaster ExamplePE=250JKE=

0At the top:Coaster has all

PETotal energy 250J

At the lowest point: all

KETotal energy 250J

PE=

0

KE=

250J

In the middle:Some KE and some

PETotal energy 250J

PE=

125J

KE=

125J

Where does the roller coaster get its PE to begin with?

WORK! The chain does work

to get the coaster to the top of the first

hill.

Describe the energy at the labeled points.

A

B

C D E F

What can you say about the total energy of the

system?

Work-Energy Cycle:Work PE KE Work,

heat, sound, etc.

•Man does_____lifting weight

work______ turns into ____work P

E

•Man releases weight, ___ turns into _____

PEKE

stake into ground, also generating _____ and ______

•Weight hits ground, does _____ driving

work hea

tsound

Where do the mallets have

KE?

Where do the mallets have PE?Where is WORK

being done?

•What kind of energy does the guy start with?

•Where does this energy come from?

•What happens to the energy as he is falling?

•Where does all the energy go in the end?

What energy transformations do you

see in this clip?

What kind of energy transformations do you see happening here?

What energy transformations do you

see in this clip?

Quick Quiz (Vocabulary)

• 1. ________ can be defined as the ability to do work.

• 2. The energy of motion is called_______.

• 3. The internal motion of the atoms is called_________.

• 4. The nucleus of an atom is the source of ________.

• 5. __________ is energy of position.

`

What energy transformations do you

see in this clip?

Forms of Energy

• Mechanical energy: Matter that is in motion has energy. Mechanical Energy is any object that is moving or could move.

• Examples - water in waterfall, blood flowing through your blood vessels.

Forms of Energy• Thermal Energy (heat): All matter

is made of tiny particles called atoms that are constantly moving. The internal motion of the atoms is called heat energy.

• The faster the particles move, the more thermal energy is produced.

• Heat energy often comes from friction or light hitting an object.

Forms of Energy

• Chemical energy: Energy exists in the bonds that hold atoms together. This energy is called chemical energy.

• When fuel is burned, chemical energy is released and converted into thermal energy.

• Ex- start a fire in a charcoal grill; digest food

Forms of Energy

• Electrical energy: Energy associated with moving electrons. These moving electric charges have the ability to do work.

• Ex- power lines; electric motors; electric lights

• Electromagnetic energy: energy of moving photons or waves of light.

• Ex- visible light; lasers; infrared; ultraviolet; x-rays; radio waves; microwaves.

Forms of Energy

• Nuclear energy: the nucleus, or center of an atom is the source of nuclear energy.

• Nuclear energy is released when lightweight nuclei collide at high speeds and fuse.

• Nuclear energy is released in the form of heat, light, sound, and mechanical energy.

• Nuclear energy is most concentrated form of energy.

• All energy untimately comes from nuclear energy.

Other Forms of Energy

• Sound Energy- waves of energy moving through matter

• Gravitational Energy- any object that could fall, roll, or slide down

What energy transformations do you

see in this clip?

Questions to Answer

• 1. What is energy?• 2. Can energy be transferred from

one object to another? Explain.• 3. What are different forms of

energy?• 4. Why is energy measured in same

unit as work?