Crossword puzzle physics

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Across
  1. 2. The extent or measurement of a surface
  2. 4. Directional speed of an object in motion
  3. 6. A unit of force
  4. 9. Force of attraction between two objects
  5. 11. A steep surface
  6. 12. The extent of something
  7. 13. A tendency to remain unchanged
Down
  1. 1. A reduction in the speed
  2. 3. Quantity with two independent variables
  3. 5. Something that remains relatively still
  4. 7. strength or energy attributed to action or movement
  5. 8. Amount of matter in an object
  6. 10. The relative mass contained by an object