Conservation of Conservation of EnergyEnergy

How did you get to school today?How did you get to school today? If you walked, did you get tired? Why If you walked, did you get tired? Why

do you think you got tired?do you think you got tired? If you rode in a vehicle, did the If you rode in a vehicle, did the

vehicle ever just shut down and stop vehicle ever just shut down and stop for no reason?for no reason?

EnergyEnergyYou were able to travel this morning You were able to travel this morning

because of because of Energy.Energy.

This is the ability or capacity of any physical This is the ability or capacity of any physical system to do system to do WorkWork. .

All work is done by All work is done by Energy.Energy. Since there are Since there are so many different kinds of forces, energy so many different kinds of forces, energy often takes on many different forms.often takes on many different forms.

Two BASIC Forms of EnergyTwo BASIC Forms of EnergyThere are two basic forms of energy: There are two basic forms of energy:

Kinetic EnergyKinetic Energy and and Potential EnergyPotential Energy. .

2 Basic Forms of Energy2 Basic Forms of EnergyAll types of energy fall under All types of energy fall under

these two categories (forms). these two categories (forms).

Kinetic Kinetic Energy are forms of Energy are forms of energy in motionenergy in motion

Potential Potential Energy are forms of Energy are forms of energy that are stored.energy that are stored.

Mechanical EnergyMechanical Energy

Mechanical energy is due Mechanical energy is due to the position and motion to the position and motion of the object.of the object.

What happens to the What happens to the mechanical energy of an mechanical energy of an apple as it falls from a apple as it falls from a tree?tree?

Energy ChangesEnergy Changes

As the apple falls to the ground, its height As the apple falls to the ground, its height decreases. Therefore, its GPE decreases. Therefore, its GPE decreases.decreases.

The potential energy is not lost… it is The potential energy is not lost… it is converted into kinetic energy as the converted into kinetic energy as the velocity of the apple increases.velocity of the apple increases.

What happens to the mechanical What happens to the mechanical energy?energy?

Mechanical EnergyMechanical Energy

The energy in the system remains constant The energy in the system remains constant – the same!!– the same!!

Swinging AlongSwinging Along

Think about the changes in energy when Think about the changes in energy when you are on a swing…you are on a swing…

At what point do you have the most At what point do you have the most potential energy?potential energy?

At what point do you have the most At what point do you have the most kinetic energy?kinetic energy?

What happens to the mechanical What happens to the mechanical energy?energy?

But how? If I stop pumping while I’m But how? If I stop pumping while I’m swinging, I stop!! So, where’s the swinging, I stop!! So, where’s the energy?energy?

Mechanical EnergyMechanical Energy

The energy in the system remains constant The energy in the system remains constant – the same!!– the same!!

Energy ChangesEnergy Changes

You need to remember frictionYou need to remember friction……

As you slow down on the swing, the As you slow down on the swing, the hooks and the chain rub against each hooks and the chain rub against each other and air pushes against the rider.other and air pushes against the rider.

Friction causes some of the Friction causes some of the mechanical energy of the swing mechanical energy of the swing to change to thermal energy.to change to thermal energy.

Thermal Energy or Thermal Energy or heat,heat, is is the kinetic energy of the kinetic energy of particles of matter. particles of matter.

Thermal EnergyThermal Energy

It is the heat caused by the friction of the It is the heat caused by the friction of the molecules moving fast and bumping into molecules moving fast and bumping into each other. That’s why it is each other. That’s why it is kinetickinetic

Changing Forms of Changing Forms of EnergyEnergy Energy is most noticeable as it Energy is most noticeable as it transforms from one type to another.transforms from one type to another.

Electrical energyElectrical energy comes from the comes from the movement movement of electrons.of electrons.

Do you think electricity is potential or Do you think electricity is potential or kinetic energy?kinetic energy?

Kinetic!

Examples of Electric Examples of Electric Energy Converting to Energy Converting to another kind of Energyanother kind of Energy

Radio electric to sound energyRadio electric to sound energy Lightbulb, electric to light or thermal energyLightbulb, electric to light or thermal energy Hair dryer, electric to thermal energyHair dryer, electric to thermal energy

Changing forms of Changing forms of EnergyEnergy Chemical Energy Chemical Energy is the is the

energy that holds bonds energy that holds bonds between atoms together. This between atoms together. This is potential because you don’t is potential because you don’t get the energy until youget the energy until you break break the bonds.the bonds.

Chemical EnergyChemical Energy

An example of transforming chemical An example of transforming chemical energy is a car engine. Chemical energy is a car engine. Chemical potential energy in gasoline is potential energy in gasoline is transformed into kinetic energy of transformed into kinetic energy of the car as it movesthe car as it moves

Energy in Your BodyEnergy in Your Body

Even the energy converted in your body Even the energy converted in your body follows the law of conservation of energy.follows the law of conservation of energy.

Chemical potential energy is transferred Chemical potential energy is transferred to kinetic energy that allows your body to to kinetic energy that allows your body to move!!move!!

Mechanical EnergyMechanical Energy

The energy in the system remains The energy in the system remains constant!!constant!!

KE and PEKE and PE

In many situations, there is a conversion In many situations, there is a conversion between potential and kinetic energy.between potential and kinetic energy.

The total amount of potential and kinetic The total amount of potential and kinetic energy in a system is called the energy in a system is called the mechanical energymechanical energy

Mechanical energy = PE + KEMechanical energy = PE + KE

The Law of Conservation The Law of Conservation of Energyof Energy The Law of Conservation of Energy The Law of Conservation of Energy

states that energy cannot be created states that energy cannot be created or destroyed. It can only be or destroyed. It can only be transformed!transformed!

The big picture… the total energy in the The big picture… the total energy in the universe remains constant.universe remains constant.

Conservation of EnergyConservation of Energy

Energy is transformed… not destroyed!!Energy is transformed… not destroyed!!