48 OUTLINES OF NATURAL PHILOSOPHY. 



able about a fixed centre, A will descend, and will 



^ jj 



be accelerated by a force proportional to -T-^T-TJ , 



or to the difference of the weights divided by their 

 sum. 



If the natural force of gravity be expressed by g, the 

 velocity which it generates in a second ; then the 



acceleration of the bodies will be A . -p x g- 



We may therefore diminish the intensity of gravita- 

 tion at pleasure, or produce an accelerating force 

 less than the force of gravity in any assigned ra- 

 tio. 



It is on this principle that Mr ATWOOD'S machine for 

 reducing the theory of accelerated motion to the test 

 of experience, is contrived. 



The acceleration of falling bodies was discovered by 

 GALILEO, Dlalogo in. de Motu locali, Ojpere, torn. 3. 

 p. 98. edit. Padova, 1744. 



SECT. 



