How do you convert newtons to weight and weight back to newtons?

Question

I know it sounds confusing but this is how it works you have to divide by 9.8 and convert to grams and then more math stuff. But every time i do that and then go backwards it didn't work!

Answer 1

Newtons are a unit of weight (or more generally, a unit of force. Weight is simply one type of force - the force due to gravity). Therefore, you don't have to do anything to convert Newtons to weight.

Edit: sigh. I do wish more schools would explain to students that grams are a unit of _mass_, not weight. And stop asking them to "convert" between Newtons and grams - or at least, state the problem in the form "find the weight of object x in Newtons given that it's mass is y grams" instead of such misleading language as "object x 'weighs' y grams, what is its weight in newtons" - sadly, most physics tests don't put "weighs" in quotes even though grams are not a unit of weight, and it is absolutely meaningless to say that something "weighs" 5 grams. Am I 34 seconds tall? Is my density 15 Pascals? Do I use 110 Hz of power? If you mean mass, say MASS, not wieght.

Oh sorry, I don't mean to take it out on you. You're not the one responsible for this mess. Anyway, to find the mass of the object, given that it weighs x newtons on the Earth's surface, you use Newton's second law:

F=Ma

(yes, mass is more frequently denoted with little m, but I want to avoid a possible confusion with meters in a moment),

Along with the fact that the acceleration due to gravity is about 9.8 m/s² everywhere on the Earth's surface. So we then do some simple algebra to find:
M=F/(9.8 m/s²)

Note that 1 newton of force is 1 kg m/s², so a weight of x newtons will result from a mass of x/9.8 kg. To get mass in grams, you would then have to multiply by 1000 (which may be where you're screwing up - you aren't converting from kilograms to grams at the end). Conversely, to find the weight, you multiply the mass in kilograms by 9.8 m/s².

Does that help?

Answer 2

Newtons is a unit of force and weight is a force so there is no conversion from "newtons to weight." If you want to convert from weight (newtons) to mass (kg) you need to divide by the accerleration of gravity as weight is the force caused by an objects gravitational attraction to the Earth.

Answer 3

Are you trying to find the mass from the force in newtons? Mass and weight are separate:
Force or Weight (newtons) = mass (kg, g, etc.) x acceleration due to gravity (9.8 m/s^2) (also called g)

Mass = Weight / g

Answer 4

Weight is mass times acceleration due to gravity, but you have to pay attention to units.

A Newton is 1 kg (1 meter/second^2)
A dyne is 1 gram (1 cm/second^2)
At the earths surface the acc due to gravity is 9.8m/sec^2


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Answer 5

Since both are forces, no conversion is necessary, except possibly to change units.