EnergyEnergy

What is energy?What is energy? Every Every changechange that occurs… big or that occurs… big or

small… requires energy.small… requires energy.

When something is able to When something is able to changechange its environment or itself, it has its environment or itself, it has energy.energy.

Energy is the ability to cause Energy is the ability to cause changechange..

Examples…Examples…

What are some What are some examples of having or examples of having or using energy?using energy? A moving baseballA moving baseball Combing your hairCombing your hair Walking up the stairsWalking up the stairs

Different FormsDifferent Forms

There are There are different formsdifferent forms of energy. of energy. When you turn on a light, the room gets When you turn on a light, the room gets

brighter.brighter. When you turn on your stereo, you hear When you turn on your stereo, you hear

sound.sound.

Think of money…Think of money…

If you had $100, you can keep it…If you had $100, you can keep it… In your walletIn your wallet In a bank accountIn a bank account In travelers checksIn travelers checks In gold and silver coinsIn gold and silver coins

The same is true for energy!! It can be The same is true for energy!! It can be found in found in different formsdifferent forms..

Kinetic EnergyKinetic Energy

Kinetic energy is energy in the form of Kinetic energy is energy in the form of motion.motion. Wheels spinningWheels spinning A sprinting runnerA sprinting runner A train movingA train moving

Kinetic EnergyKinetic Energy

Kinetic energy depends on two Kinetic energy depends on two quantities…quantities… The mass of the moving objectThe mass of the moving object The object’s velocityThe object’s velocity

Kinetic EnergyKinetic Energy

The more mass an object has, the more The more mass an object has, the more kinetic energy it has.kinetic energy it has.

The greater an object’s velocity is, the The greater an object’s velocity is, the more kinetic energy it has.more kinetic energy it has.

Kinetic EnergyKinetic Energy

Which one has the most kinetic energy?Which one has the most kinetic energy?

Velocity = 5 m/s

Mass = 500 kg

Velocity = 20 m/s

Mass = 500 kg

Kinetic EnergyKinetic Energy

Kinetic energy is measured in joules (J)Kinetic energy is measured in joules (J) We use the following equation to We use the following equation to

calculate how much kinetic energy an calculate how much kinetic energy an object has:object has:

Kinetic Energy = ½ (mass) x (velocity)Kinetic Energy = ½ (mass) x (velocity)22

KE = ½ m vKE = ½ m v22

KE (joules) = ½ m (kg) x vKE (joules) = ½ m (kg) x v2 2 (m(m22/s/s22))

RacecarRacecar

If a racecar with a mass of 800kg is If a racecar with a mass of 800kg is traveling at 35 m/s… how much kinetic traveling at 35 m/s… how much kinetic energy does the car have?energy does the car have?

KE = ½ mvKE = ½ mv22

KE = ½ (800kg) x (35 m/s)KE = ½ (800kg) x (35 m/s)22

KE = 490000 J or 490 kJ KE = 490000 J or 490 kJ

Potential Energy (PE)Potential Energy (PE) Even motionless objects can Even motionless objects can

have energy… the energy is have energy… the energy is stored in the object.stored in the object.

An apple hanging in a tree has An apple hanging in a tree has potential energy because it has potential energy because it has the ability to cause change, to the ability to cause change, to fall to the ground.fall to the ground.

Stored energy due to a position Stored energy due to a position is called potential energy (PE).is called potential energy (PE).

Elastic Potential EnergyElastic Potential Energy

Elastic potential Elastic potential energy is energy energy is energy stored by something stored by something that can stretch or that can stretch or compress such as a compress such as a rubber band or a rubber band or a spring.spring.

Chemical Potential Chemical Potential EnergyEnergy

Energy stored in chemical bonds Energy stored in chemical bonds is called chemical potential is called chemical potential energy.energy.

Chemical energy is stored in Chemical energy is stored in bonds that hold a molecule bonds that hold a molecule together and are released when together and are released when the bond is broken.the bond is broken.

Gravitational Potential Gravitational Potential EnergyEnergy Gravitational potential Gravitational potential

energy (GPE) is stored by energy (GPE) is stored by objects that are above the objects that are above the Earth’s surface.Earth’s surface.

The amount of GPE The amount of GPE depends on:depends on: The mass of the objectThe mass of the object The acceleration due to The acceleration due to

gravitygravity The height above the The height above the

groundground

Gravitational Potential Gravitational Potential EnergyEnergy To calculate the GPE of an object, To calculate the GPE of an object,

we use the following equation:we use the following equation:

GPE = mass x gravity x heightGPE = mass x gravity x height GPE = mghGPE = mgh GPE (J) = m (kg) x g (m/sGPE (J) = m (kg) x g (m/s22) x h (m)) x h (m)

Changing GPEChanging GPE

The GPE of an object can be The GPE of an object can be changed by changing the changed by changing the height of the object.height of the object.

When the height of the object When the height of the object is increased, the gravitational is increased, the gravitational potential energy increases!!potential energy increases!!