motion and time

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Across
  1. 1. the distance covered by a moving object in unit time is known as?
  2. 2. 10 centuries is how many years
  3. 4. nowadays wrist watches have a ______ instead of a pendulum
  4. 6. what is the length of a pendulum that takes exactly 1 second for to & fro motion
  5. 7. what is the commonly used unit of temperature
Down
  1. 1. the abbreviation of SI
  2. 3. what kind of clock did the romans mostly use
  3. 5. which kind of instrument measures time more accurately