## tanvirms 2 years ago hi. we know gravitational force F is prop. to m1m2, it is also inversely prop. to d^2, we then combined these two proportions and wrote that F is prop. to m1m2/d^2. How can we do that? does that mean if x is prop to a, and x is prop to b, then x is prop to ab? im confused.

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1. surdeep

i think if x is prop to a & x is prop to b then, a is prop to b...!!!

2. Mashy

YES.. if x is proportional to a and proportional to b, then it does mean its proportional to ab .. let me explain how if x prop to a.. that means when a doubles x doubles, when a triples, x triples.. a halves, then x halves and .. i hope you get the point.. and the same is with x and b as well so now consider the product ab, when a doubled and b doubled.. ab has become four times.. and we know x has become 4 times as well (cause x doubled cause of a and then doubled again cause of b).. so isn't now x prop to ab? :)

3. Mashy

and surdeep what you mentioned is not only wrong but is preposterous :P.. a and b could be totally independent of each other .. so they would have no relation with each other what so ever :P.. take gravity for example.. mass and distance have no relation whatsover :P

4. surdeep

oh thanks for the info Mashy