Energy The ability to do work Work is done when a force moves an

object over a distance

Potential Energy Stored energy an object has due to its

position.– Ex: A rock on top of a cliff has potential

energy because of its position above ground level

– Ex: A lump of coal contains potential energy in its chemical bonds, causing fire when exposed to a flame

Kinetic Energy Energy of motion

– Ex: A rock falling off a cliff– The heat given off by a burning lump of

coal– The faster an object moves, the more

kinetic energy it has

Energy Potential energy may be changed into

kinetic energy when an object begins to move– Ex: Water held back by a dam has

potential energy but no kinetic energy. Releasing the water and letting it flow changes its potential energy into kinetic energy.

Energy Kinetic energy may also be changed into

potential energy– Ex: When a ball is thrown straight up in the air,

its kinetic energy changes into potential energy as the ball rises higher above the ground. At the highest point, the ball is motionless and has only potential energy. As the ball falls back to the ground, the potential energy changes back into kinetic energy.

Forms of Energy There are 6 forms of energy

– Mechanical– Chemical– Nuclear– Heat (thermal)– Electric– Light (radiant, electromagnetic)

Mechanical Energy Energy with which moving objects

perform work– Ex: hammer striking a nail, a jack lifting a

car, pedals turning the wheel of a bike– Sound is a type of mechanical energy

Chemical energy Energy stored in certain substances

because of the make up of their chemical bonds– Ex: coal, oil, natural gas, food

Nuclear energy Energy stored within the nucleus of an

atom– Joining small nuclei together or splitting

large nuclei apart

Heat Energy Produced by the molecular motion of

matter– Ex: rubbing your hands together, cellular

respiration, burning fuel oil in a home

Electric Energy Produced by the flow of electrons

through a conductor, such as a wire.– Ex: computers, light bulbs, washing

machines all are operated with electric energy.

– A generator produces electric energy.

Light Energy Form of radiant energy that moves in

waves– Ex: magnifying glass burns a hole in a

leaf or using a laser beam to burn a hole in a steel plate.

Conservation of Energy The law of conservation of energy

states that energy can neither be created nor destroyed.

Energy can easily be transformed from one type of energy into another type of energy

Conservation of Matter The law of conservation of matter

states that matter can neither be created or destroyed. Energy and matter are interchangeable. The total amount of energy and matter in the universe is constant and each can be converted into the other.– Ex: The sun converts large amounts of

matter into light and heat energy

Energy Transformations Ex: when you take a bus to school, chemical

energy in the gas is changed into mechanical energy that turns the wheels of the bus

Ex: The bell rings between classes, electric energy is transformed into sound energy

Ex: At night when you are reading, electric energy is changed into light energy

Unusable Energy During energy transformation heat

energy is produced that is not usable.– A cars motor changes chemical energy in

gas into mechanical energy to move the car. The motor eventually becomes hot due to the burning of fuel and friction of the motors moving parts rubbing against one another

Unusable Energy Ex: a vacuum cleaner contains a motor

that transforms electric energy into mechanical energy. Run a vacuum cleaner for a few minutes and it gets warm. The electric energy entering the motor produced mechanical energy to operate the appliance and an unusable amount of heat energy.