I know that weight changes depending on the amount of gravity, but what are we measuring when we use a newton metre? Is it mass, or weight?
Mass and weight OE force are related by Newton's Second Law of Motion, which states that force (or weight, in this case) is equal to the product of mass of a body and its acceleration. In other words,
The unit of mass is kg(typically), acceleration is m per square second and force is measured in Newton.
So when we use kilogram, we are measuring mass and when we use Newton, we measure force or weight. Remember, weight is a measure of gravitational force, I.e. acceleration in this case is the gravity. And hence weight will change as the gravity changes.
When we use newton meter, we are not measuring mass or weight, we are actually measuring energy or work. Energy or work is defined as a force of 1 newton acting through 1 meter and hence the units are newton- meter.
Hope it helps.
As the previous person said, mass and weight are related.
When you use a Newton meter it is measuring Force. But with any weight measuring device it stretches or compresses a spring in the device moving the arrow to a certain output based on the spring. So either way, it is measuring force!