Beginning of Human Civilization

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Across
  1. 3. a device that increases or decreases the voltage of an electrical current.
  2. 5. two__________________-something flat that exists in 2 directions; height and width.
  3. 7. waves ultrasound are ___________ ___________that are smaller, or of a higher frequency, than can be heard by human beings.
  4. 10. searched for food.
  5. 11. Rockets were first developed over 2000 years ago in ___________________________.
  6. 13. ________________________________ can be measured in amps and volts.
  7. 16. a method of using sound waves to locate and identify objects.
  8. 19. An Internal Combustion Engine is an engine that is powered by the energy of___________________.
Down
  1. 1. gas that leaves an engine.
  2. 2. a medical or scientific tool used for investigating.
  3. 4. people without a permanent home who travel from place to place.
  4. 6. an ancient culture located in the area that is Iraq today.
  5. 8. a short tube that becomes narrower on one end.
  6. 9. the last part of the stone age.
  7. 12. may be the most important process that human beings ever developed.
  8. 14. safe to eat.
  9. 15. Compared to x-rays, which use a form of _______________________________ultrasound is much safer.
  10. 17. _________dimensional-something solid that exists in three directions; height, width, and depth.
  11. 18. military rockets that carry explosives to their targets.