force and friction

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Across
  1. 2. example of contact force
  2. 3. is a device to measure force
  3. 4. friction generates
  4. 6. friction occurs due to _ of irregularities
  5. 7. friction is a neccessary _
Down
  1. 1. example of non contact force
  2. 2. the effect that a contact force has depend on the _ force
  3. 5. push or pull