What makes a roller coaster go fast?

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Across
  1. 2. transfer when energy travels from one place to another
  2. 6. energy that is in the form of sound that can be heard
  3. 7. energy that is due to gravity
  4. 8. when one object hits or crashes into another object
  5. 9. how fast something is moving
Down
  1. 1. an invisible force that pulls any object down toward the Earth
  2. 3. a test used to discover new information about a question
  3. 4. repeated tests in an experiment
  4. 5. energy that is not in use but is saved inside something (battery)