Potential and Kinetic Energy

What is Energy?Energy is the ability to cause change.

Everything except feelings and ideas is made up of energy or matter. Energy does not have mass or take up space.

Which of the examples below are energy?

Air Light Love Atoms Heat

Potential EnergyEnergy that is stored in matter, waiting to be

released.

Examples:

What similarities do you notice about all these examples?

An arrow being stretched by a bow before it’s released

A rock at the top of a hill

Food for our bodies.

Fuel for our automobiles

Kinetic EnergyThe energy of motion that is released from stored

energy.

Examples:

What similarities do you notice about all these examples?

An arrow released from the bow, flying through the air.

An object rolling down a hill.

Muscles moving.

A car moving.

Potential and Kinetic EnergyEnergy can change from potential energy to kinetic

energy.

Examples:

But height is not the only way for potential energy to change to kinetic energy. Can you think of any?

A yo-yo goes from P.E. to K.E. as it goes up and down.

A biker goes from K.E. to P.E. to K.E. as he goes up and down a hill.

A roller coaster goes from P.E. to K.E. as it rolls down a hill.

Potential and Kinetic EnergyMolecules store energy in their bonds, which can be broken to

release energy. This is happening to you right now, as the food you have eaten is going through a chemical change to release energy!!

Examples:

a

When you eat, your digestive system breaks down food into molecules that are sent to every cell in your body, where they are broken down to release energy which you need to live!

Gasoline is food for your car. When you burn gasoline, the molecules break down releasing energy and burning, giving the car what it needs to move!

Energy in Food Food can be measured by the amount of energy it has. For example, a piece of buttered toast

has about 315,000 Joules of energy. With that energy you could: Jog for 6 minutes Bicycle for 10 minutes Walk briskly for 15 minutes Sleep for 1 ½ hours Run a car for 7 seconds at 50 mph Light a 60 Watt bulb for 1 ½ hours Lift a sack of sugar from the floor to the counter 21,000 times!

Other Examples:

a

Roller CoastersWatch the roller coaster from:

http://www.funderstanding.com/coaster

Answer the following questions:1. Why didn’t the roller coaster make it all the

way through at first?2. What could you change to make it work?

(include all possibilities).

a

Roller Coaster ProjectChallenge: design and create a roller coaster that lets

the marble travel all the way through.

Requirements: Marble must land in the cup at the end of the roller coaster The roller coaster must have at least 1 hill and 1 loop You must include a diagram with PE and KE labeled You must record the length of the roller coaster, time it takes for the

marble to go through it, mass of the marble, and height of the first hill. You must calculate speed of the marble, and potential energy using

formulas. You must conduct 5 trials You must answer the conclusion questions At the end of the project you will create a poster showing your design

and how you have applied your understanding of potential and kinetic energy.

Forces on the Roller Coaster What forces are acting on the roller coaster

that might affect its speed?Friction

Gravity

- due to surfaces touching- the frictional force on the roller coaster is between the track and the marble.- Air resistance may also be included here

- due to the pull of gravity to the center of the Earth.- the gravitational force pulls the marble down

This arrow represents friction. It is pushing against the movement of the roller coaster.

This arrow represents gravity. It is pushing down on the roller coaster.

Be prepared to draw arrows representing friction and gravity on your roller coaster poster

Representing PE and KE Use a bar graph to represent potential energy

(PE) and kinetic energy (KE) at different places on the roller coaster.

A

B

C

D

At point A, a bar graph for PE and KE would look like this:

What would a bar graph look like for points B, C and D?

Be prepared to label important areas for PE and KE on your roller coaster poster.