Question

can anyone give me or show me how to prove
weight= mass* gravity? please

Answer 1

@experimentX

Answer 2

are you trying to prove f=ma?

Answer 3

no

Answer 4

i am thinking and striving to prove weight = mass*gravity? how, i was pondering over it

Answer 5

this comes from definition ... weight = gravitational force.
weight = GmM/R^2 = m GM/R^2 = mg

Answer 6

this is my question how weight = gravitational force* mass (not weight @experimentX :) )

Answer 7

and i heard that there is a long proof of it i am looking for that

Answer 8

weight = gravitation force = m g
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well i guess there is since there is lot's of confusion around mass since the definition of mass keeps going round and round around force and inertia. I haven't understood it correctly.

Answer 9

probably to clear out this circular logic of mass. but weight = mg ... this comes from newton's second law.

Answer 10

weight= mass* acceleration due to gravity
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probably you made mistake here ... gravity would mean different thing.

Answer 11

@experiment i need mathematical explanation of this definition how weight = mass*gravity?

Answer 12

There is no mathematical derivation. That the force exerted by gravity on an object is proportional to its mass is a hypothesis of Newtonian gravitation, confirmed by experiment. It's an observation, not a deduction.

Answer 13

@carl_pham everything in this universe has a mathematical explanation and i strongly believe it has some mathematical explanation and it is in the book principia mathematica by newton , albeit i tried hard to understand that but unfortunately i couldn't and once again i must say there is a derivation of this but unfortunately i am unable to find it.

Answer 14

I was writing it for 10 minutes and the page reloaded

Answer 15

The thing is, \[F=ma=mGMr^{-2}\]if we notice that we are considering the weight only for objects very close to the surface of the earth, we see that GMr^-2=g and even though this radius usually change, we can consider it as constant and equal to the radius of the earth, therefore getting the acceleration g.
A more formal explanation involves the same concept, we take a taylor expansion around the radius of the earth of the function GMr^-2=g(r) and consider only the first term since we r and the radius of the earth are very close. This provides a more clear view of whats going but is really unnecessary. It is not useful to continue the taylor expansion to include greater heights because the function F is really simple.

Answer 16

@ivanmlerner your explanation seems precised . thanks

Answer 17

@ghazi, and interesting faith, but unfortunately you are wrong. Anything derived purely from empirical observation has no mathematical derivation at all. It just is. Obvious examples include the value of the fine structure constant, as well as many other important constants, why the nuclear forces have a finite range, and the Second Law of thermodynamics (the one that says the entropy of the universe is always increasing). Not one of these things has a mathematical, or indeed any explanation. They are simply observable facts that characterize this universe.

Answer 18

agreed, but i'll get you that soon