What does the weighing scale we use in our homes actually measures? As weight should be in Newton and it measures in Kilograms so does it measures our mass ? Why we say that our weight is x Kilograms when we should say the weight is x Newtons , it is too confusing for me .

Question

What does the weighing scale we use in our homes actually measures? As weight should be in Newton and it measures in Kilograms so does it measures our mass ? Why we say that our weight is x Kilograms when we should say the weight is x Newtons , it is too confusing for me .

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Answer 1

Whenever you have a measuring device you only know what it measures but how it provides you data is at first is a bit unknown. Its some number that contains information about the thing you measure. With a scale you measure weight.

So you place an apple on the scale and it outputs 618. That is the weight but we would like that information to be in a way it makes sense. So we know we weight is measured in Newtons but there is a correlation between mass and weight through gravitational acceleration.

So lets start by turning that 618 into Newtons. We grab weights we know. Lets say we have measure the gravitational acceleration in the lab and now we know that the weight of object 1 is 1N object 2 is 5N and object 3 is 10N. Lets put 1 one the scale and it outputs 629, then 2 giving us 3145 and 3 for 6290.

So when we plot the known weights in Newtons as a function of the scale’s output we get a 3 points that are all on a line in this case, we can say that we got a linear relationship so lets fit a line. y=m×x. x is what the scale outputs and y is the weight in Newtons, m is the conversation factor. Here that would be m = 1/629.

So now when the scale outputs a number we can convert it to a weight in Newtons. That is calibration. If we want to turn that to mass we often take g=9.81m/s² its g around 45° latitude. And lets multiply m with 1/g to give us the conversation factor between the scales output and mass.

If its an analog scale we just make the numbering of the scale in that way if its digital we just output the converted amount.

So you don’t know the connection between the things your measuring equipment outputs and the things you measure, thats what calibration is for to find this connection. After that you can make the equipment outputs anything.