• How much energy is one Joule?

• Not much!– One Joule is the amount of

energy it takes to lift a small apple to a height of one meter on the earth

– Often we talk about kiloJoules, thousands of Joules

What is energy?•Energy is the Energy is the ability to do ability to do workwork•The unit of energy is the Joule, The unit of energy is the Joule, named after James Prescott named after James Prescott JouleJoule

•This is also the unit of work, This is also the unit of work, since energy and work are since energy and work are manifestations of the same manifestations of the same thingthing

http://dspt.club.fr/PortraitJoule.jpg

• Mechanical-Kinetic and Potential

• Light

• Electrical

• Nuclear

• Heat

• Chemical

Energy can take many forms

Chemical Energy

• Type of potential energy

Electrical Energy

Electromagnetic Energy

Nuclear Energy

Radiant or Light Energy

• Solar energy

Light Energy

Sound Energy

Thermal Energy

Mechanical Energy

• This type of energy is called gravitational potential energy (abbreviated potential energy).

Chemical potential energy is in a fuel such as a

match.

KINETIC ENERGY

Energy of Motion

Law of Conservation of Energy

Energy cannot be created nor destroyed

but can converted into another form of

energy.

Energy is conserved• It may change forms

but you cannot lose energy

• A falling apple illustrates the relationship between potential and kinetic energy– You can convert it to a

form that does not do work such as heat lost as friction

Potential energy decreases as it falls

Kinetic energy increases as it falls

Chemical Potential Energy Electrical Energy Light

Energy

Food is a type of fuel.

Chemical potential energy Kinetic energy

Sound energy electrical energy sound energy

Chemical potential energy heat and

kinetic energy

Electrical energy heat and light energy

Electrical energy light and sound

energy

Chemical potential energy light and

heat energy

• Electrical energy may power a light bulb and be converted to light energy.

• The light energy also produces heat energy.

• Einstein's equation shows this relationship.

• E = Energy (Joules)

• m = mass (kg)

• c = speed of light (300,000 km/s or 3 x 108 m/s)

• The two most common energy conversions are:

• Potential energy changing into kinetic energy.

• Kinetic energy changing into potential energy.

Thermal Energy

           

Heat Transfer

Conduction

• Transfer of heat energy from one solid object to another when they are in direct contact.

• Metals and other materials that readily (easily) transfer heat energy through themselves are called conductors.

• Materials that transfer heat energy poorly are called insulators.

Convection

• Process of heat transfer in fluids (liquids and gases) by means of rising and falling currents.

• When a region of liquid or gas absorbs heat energy, its molecules move faster, and the distance between them increases.

• The region of fluid expands as a result and becomes less dense than its surroundings.

Radiation

• Transfer of heat energy in the form of electromagnetic waves

• The same kinds of energy waves transfer heat and light energy from the Sun as it radiates energy to Earth.

• Electromagnetic waves travel through the emptiness of space.

• They can also pass through many types of matter.

• Infrared electromagnetic waves are sensed by nerves in the skin as heat.

• All warm bodies radiate heat energy in the form of infrared electromagnetic waves.

• When you sit near a fireplace, you can feel the effect of these waves warming you.

• Toaster ovens heat and toast bread and other food products by radiation.

A bird in your hand, 1 m above

the ground

The same bird on the limb of a tree, 5 m above

the ground

OR

In which case would the object have

more potential energy?

OR

A tennis ball, sitting on a shelf 2 m above the

ground

A softball, sitting on a shelf 2 m

above the ground

In which case would the object have

more potential energy?

OR

A beach ball, rolling at a

speed of 2 m/s

A bowling ball, rolling at a

speed of 2 m/s

Which object has greater kinetic energy?,

OR

A golf ball, flying through the air at a speed of 10 m/s

A golf ball, flying through the air at a speed of 15

m/s

Which object has greater kinetic energy?,