see my question below...(it's kinda long so i put it on the question details part)....?

Question

Although the distinction between mass and weight may seem trivial on the surface of the earth, it can be a matter of life and death in space. Suppose a space station is being built in orbit around the earth. Astronauts building the station are moving huge girders into position in the space station.
are these girders weightless?
if they are weightless, are they any easier to move around in space than they would be on earth?
could an astronaut be crushed to death between two huge girders moving toward each other in space, even if they were weightless?

Answer 1

To A and B: The girders are indeed weightless. They are in "free-fall" which means that they are accelerated by gravity in the same direction and magnitude as the astronauts are. So the astronauts do not feel any weight from them.
To C: The girders may be weightless, but they still have mass. Even in zero gravity, mass can still do damage. A girder that weights 980 kg on earth will still have 100 kg of mass in space and if that hits an astronaut in the chest at any speed, it will certainly knock the wind out of him and may even snap his safely line and send him spinning off into space. It is just as likely to rip his suit and expose him to space. This is just part of the reason why in spite of the weightless environment, astronauts and cosmonauts are very very careful when spacewalking and move very slowly.

Answer 2

A. Yes.

B. No. Inertia applies regardless. F=ma. A massive object like a girder, would require a significant force to induce an acceleration. Once moving, though, it will continue to move until an opposing force stops it. So in that respect, you are not always fighting gravity, but conversely you don't have gravity helping either. It's probably close to a zero-sum game so I think there is no difference to the amount of work required to move objects in space as opposed to on Earth.

C. Absolutely. Same as above. Depending on how fast the girders are going and how massive they are, they could definitely crush an astronaut easily. In fact, the effect would be the same as on the Earth.

Sparc77...mass does not change regardless of the gravitational frame of reference. A 980 kg girder will have the same mass in space as it does on Earth or the Moon.

Answer 3

a. yes. b. yes, although it needs to be done slowly and carefully. c. yes, definitely, they still have mass and momentum.

Answer 4

Yes

Definitely

Possible but not very likely