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? AirLightLove AtomsHeat

What is Energy? Energy can be defined as the ability to do work or cause change. Energy can be changed from one form to another. The most common energy conversion is the conversion between potential and kinetic energy.

Potential Energy ●Energy 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

What is Potential Energy? □Energy that is stored and waiting to be used later

More examples of Potential Energy Roller coaster at the top of a hill Skier at the top of a track

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

Kinetic Energy ●The 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.

What is Kinetic Energy? □Energy in motion □The faster an object moves or the more mass an object has, the more kinetic energy.

Potential and Kinetic Energy ●Energy 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 Energy ●Molecules 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!

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.

How is all energy divided? Potential Energy Kinetic Energy All Energy Gravitation Potential Energy Elastic Potential Energy Chemical Potential Energy

What is Gravitational Potential Energy? □Potential energy due to an object’s position – the higher above ground, the more potential energy stored

What is Elastic Potential Energy? □Potential energy due compression or expansion of an elastic object. Notice the ball compressing and expanding

What is Chemical Potential Energy? □Potential energy stored within the chemical bonds of an object

Roller Coasters Watch the roller coaster from: 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 Project ●Challenge: 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