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The_Radiation_Specialist
2008-Feb-12, 08:58 AM
How do you "weigh" yourself or something in space? I mean find it's mass. I've thought about it but strangely nothing has occured to me. Can you use F=m a? i.e. give it a specified force and see how much it accelerates, then find its mass?

edit: I meant microgravity.

Neverfly
2008-Feb-12, 09:52 AM
Displacement may be a way.

clop
2008-Feb-12, 09:58 AM
Maybe you could swing it round on a spring and measure the extension of the spring.

clop

Neverfly
2008-Feb-12, 10:01 AM
Maybe you could swing it round on a spring and measure the extension of the spring.

clop
And try not to hit anyone in the head.

Occams Ghost
2008-Feb-12, 10:05 AM
Black holes are predicted to form from the collapsed states of certain large stars, about several times larger than our star. They do so, because of gravitational acceleration, given by the formula;

g=(GM)/d2

Remember, a free falling object will have the force of gravity totally cancelled out as it’s that weak.
We know that from Newton’s Force Equation is derived as f= ma, where this also shows an inertial system to derive the acceleration due to gravity. So the gravitational acceleration is the mass of a gravitationally warped object M, and the distance d from it. Also, instead of working out the mass of a black hole you can work out its mass against the gravitational acceleration formula, by;

M=gd2/G

We use the same method to work out the mass of the earth. The G is Newtons universal gravitational constant (6.7×10-11 m3/(kg sec2). We find the Earth's mass = 9.8 × (6.4×106)^2 / (6.7 × 10-11) kilograms = 6.0 × 10^24 kilograms.

Jens
2008-Feb-12, 11:00 AM
Displacement may be a way.

Displacement? How so?

cmsavage
2008-Feb-12, 02:58 PM
If you put it on a spring and pushed, the vibrational frequency of the oscillations can be used to determine the mass. As long as the spring is not highly distorted, the frequency depends only on the mass and the spring constant, not on the amplitude of the oscillations. Larger masses have more inertia and take more time for the spring to turn around: the frequency goes as the inverse square root of the mass. See harmonic oscillator (http://en.wikipedia.org/wiki/Harmonic_oscillator) at Wikipedia (specifically, the "Spring-mass system" section at the end).

papageno
2008-Feb-12, 03:23 PM
You could ask ESA (http://esamultimedia.esa.int/docs/edukit_lesson_plan/inertial_balance.pdf).

Noclevername
2008-Feb-12, 08:17 PM
Or use a Forward_Mass_Detector (http://en.wikipedia.org/wiki/Forward_mass_detector#Forward_Mass_Detector)

Jeff Root
2008-Feb-13, 02:09 PM
Skylab had a device for measuring the astronaut's masses. I think it
was basically a couple of springs attached to the astronaut so that he
would extend/compress the springs, then release himself, and he would
be pulled back and forth. The period of oscillation gives the mass.
I don't know how well it worked. The ISS may have something similar.
Measurements of mass must be needed on the ISS and on Shuttle
fairly often. I didn't download the PDF that Papageno linked to, but
the ESA's Space Lab, carried on numerous Space Shuttle flights, must
have at least sometimes carried mass-measuring devices.

-- Jeff, in Minneapolis