act on vs put under an obligation

act on

verb
  • To affect something. 

  • To act decisively on the basis of information received or deduced. 

  • Το act accordingly to a (usually sublimated) desire or impulse. 

  • To take action against something. 

put under an obligation

How often have the words act on and put under an obligation occurred in a corpus of books? (source: Google Ngram Viewer )