# Kinetic Energy

## The energy of moving matter. KE = 1/2 mass X velocity 2

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Practice Kinetic Energy

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Roller Coaster Energy

### Roller Coaster Energy

Credit: Boris23
Source: http://commons.wikimedia.org/wiki/File:Rollercoaster_expedition_geforce_holiday_park_germany.jpg

What a thrilling roller coaster ride! You can almost hear the screams of the passengers. How does a roller coaster work? It’s all about energy.

#### The Back Story

• Most rollercoasters use an electric motor to move the cars up the track to the top of the first hill. As the cars move higher, they gain potential energy. Once they reach the top of the first hill, the motor is no longer needed.

Credit: Tony Hisgett
Source: http://www.flickr.com/photos/hisgett/4441109996/

The rollercoaster attains the maximum potential energy at the top of this hill [Figure2]

• The potential energy gained by reaching the top of that first hill is converted to kinetic energy of the cars rolling over the track.
• Additional hills restore some of the potential energy so the coaster can keep going.
• If you haven’t ridden on a roller coaster before or in a while, take a virtual ride on Europe’s tallest roller coaster by watching this video: https://www.youtube.com/watch?v=RzhAMvLCEno

#### Can You Apply It?

Learn more about the energy of roller coasters at the link below. Be sure to explore the animation to see how potential and kinetic energy change as the cars move over the track. Then answer the following questions.

1. The first, or lift, hill of the roller coaster gives it its maximum gravitational potential energy. What does this energy depend on? How is it calculated?
2. After the coaster starts down the first hill, how can its kinetic energy at any given point be calculated?
3. In the animation, turn off the “Energy Losses” button. As the kinetic and potential energy of the moving roller coaster change, what happens to the sum of the kinetic and potential energy? Why?
4. In the real world, a roller coaster loses some of its energy to the environment. What might be some reasons that energy is lost?
5. Use the numbered buttons to change the shape of the track. Develop one rule that must be followed to keep the cars moving all the way to the end of the track. Explain this rule.

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