Something I have wondered for a long time. And if you all will indulge me, I will even offer my own, possible solution.
But my question is simply this: How do astronauts measure mass, when they are in space, where everything is essentially weightless?
Weight is, of course, relative to gravity. But mass at rest always remains constant. I know when I was in high school, we used to measure mass, it was said, by comparing it to other masses, on a balancing scale. You can’t do that in space.
Also, I do have a partial solution myself. But I don’t know if it is even feasible. Why not, throw something in space? Then measure its mass. When something is thrown, the impact is still the same, isn’t it? Though really, I am not even sure about this. IANAPhysicist (or scientist, even).
Weight isn’t relative to gravity, it’s the measure of gravity … we can say such-and-such “weighs” 100 lbs, or we can say “the magnitude of the force of gravity is” 100 lbs … or even it weighs 500 Newtons …
Your solution has merit … if we apply a 1 Newton force to an object and then measure the acceleration … we can use Newton’s 2nd Law of Motion … F = ma … and quickly solve for mass … for a force of 1 N, we have acceleration of 1/4 m/s/s, we know the mass is 4 kg.
I had a vague recollection I did. You know, I am not as young as I used to be;). My memory is beginning slow, even now. I’m serious.
Just two things, I will say then: (1) always check, to see if your question was asked before (I hope from now on, I will:smack:); and (2) let’s rehash the question, by all means. There are some new people on the boards, I have noticed. Let’s see what they have to say, now:).
Specifically, they use a body mass measurement device which acts as a single degree of freedom oscillator; on Skylab this was known as the M172 Weight Chair as detailed in this newsletter (pg 7-9) from Tom Irvine’s Vibrationdata.com site. On the International Space Station, a similar device known as the Space Linear Acceleration Mass Measurement Device is currently used.
In high school we had an inertial balance. I’d guess that use something along those lines. I don’t think gravity would come into play with that. Here’s a video. FTR, I didn’t watch or listen to it, I just looked for a video. All I really remember from HS is that you put a mass in it, and let it oscillate back and forth and counted the oscillations for a given amount of time (or a set number of oscillations and counted the time) and from there you could calculate mass.