Does weight matter?

[witeken]

Something with a higher mass falls faster than something with a low mass. This is general known.

My question is. Does that also matter in space? I mean:

Space station A is a normal space station, flying in a circular orbit at 2000 km with a speed of x.

Space station B is the same space station, but fully filled with iridium (density of 22,56, means that 1 dm³ weighs 22,56 kg), flying in a circular orbit at 2000 km.

The mass of SSA is m. The mass of the identical SSB is 2m.

My question is now:

Is the speed of SSB x.

They are doing both a same orbit, so their speed should be equal. But SSB has the double of the mass as SSA. When you would let them fall from 5 km, SSB would hit earth as first. But I never heard something about when they\'re in orbit. What would happen then.

Ideas? Suggestions? Tips? Tricks? I rather think SSB has a speed of x. If that\'s true, I\'d very like to know why. If not, also.

[TNTGODZZ]

Something with a higher mass falls faster than something with a low mass. This is general known.

wrong. everything, yes EVERYTHING falls at the same speed.

as for your question, i dont know.

[RC1062]

As above.

Everything falls with the same acceleration in a vacuum. That\'s why everything in the same orbit has the same speed. The force acting on each would be different but as \'a = F/m\' The acceleration towards the planet is the same.

[witeken]

wrong. everything, yes EVERYTHING falls at the same speed.

I meant on earth.

[SmiteZero]

But as they said, you\'re not ON Kerbin/Earth, you\'re in space, in a vacuum. Everything falls at the same speed, only the resistance of air matters.

[mincespy]

I meant on earth.

Still would on earth, the only reason it doesn\'t is air resistance.

[RC1062]

I meant on earth.

Then it is counteracted by air resistance as opposed to mass.

[Johno]

(Science teacher mode on)

I\'m just going to use the information others have contributed, but put it into a more user-friendly format.

It actually comes as a shock to people that 'heavier' doesn\'t mean 'falls faster'. But it\'s true. You can demonstrate it for yourself fairly easily.

Grab something with a bit of mass - a large fishing sinker, for example, or a hammer - and a piece of paper. Now, if you drop both the hammer and the piece of paper, the paper floats sideways while the hammer falls straight down.

But that\'s actually because the piece of paper, for its small mass, has a very large surface area, and is therefore much more strongly affected by air resistance.

To prove it, take the same piece of paper, but this time wad it up into a ball. Now drop the paper ball at the same time as the hammer.

Yeah, it\'s surprising, isn\'t it? They hit the ground at almost the same moment. Now, on Earth you can minimise the effect of air resistance (i.e. by balling up the paper), but you can\'t eliminate it. That\'s why the feather experiment on the Moon was so significant - you can see the objects falling at EXACTLY the same speed.

Okay, so now that we know this, we understand why when an astronaut leaves the airlock of the ISS, becoming effectively a tiny separate satellite, he or she doesn\'t suddenly jerk into a wildly different orbit - if they were affected differently by gravity, that\'s what would happen! Instead the astronaut and the Space Station are falling towards the centre of the Earth, accelerating exactly the same amount.

So no, the iridium space station WOULDN\'T have its orbit decay faster.

However, there is still a very good reason to keep the mass down - every gram of extra mass requires a certain amount of propellant to get it into orbit; therefore every gram of extra mass also requires the rocket to carry enough propellant to lift the propellant to the place where it gets used, and so on. This vicious cycle was first described by the Russian scientist Tsiolkovsky. And it\'s the bane of rocket engineers\' lives - because every gram of propellant makes the rocket larger, more costly and more complex.

[witeken]

Thanks for informative posts

If I understand it right, the only reason why something is falling faster to the ground (e.g. stone vs. paper) is because of the air. Errr.... no? I can\'t imagine that if there is no air on earth, a sheet of paper will fall even fast as a stone ???.

[TNTGODZZ]

Thanks for informative posts

If I understand it right, the only reason why something is falling faster to the ground (e.g. stone vs. paper) is because of the air. Errr.... no? I can\'t imagine that if there is no air on earth, a sheet of paper will fall even fast as a stone ???.

i know it blew my mind when i was first told that, and shown that in a science lesson last year. but it is easy to get to grips with

[togfox]

Well explained johno. Witekin, watch the link posted aboce (with sound) and see for youself.

[SmiteZero]

Thanks for informative posts

If I understand it right, the only reason why something is falling faster to the ground (e.g. stone vs. paper) is because of the air. Errr.... no? I can\'t imagine that if there is no air on earth, a sheet of paper will fall even fast as a stone ???.

You\'ve never seen Armstrong drop a hammer and feather on the surface of the Moon?? ???

It\'s also a common classroom science demonstration using a vacuum chamber with a penny and feather or something of disparate weights.

All objects get accelerated by gravity at the same speed.

[Rock-it-man]

You\'ve never seen Armstrong drop a hammer and feather on the surface of the Moon?? ???

Nobody has. That was David R. Scott, mission commander of Apollo 15, not Neil Armstrong (he commanded Apollo 11).

[Phoxtane]

(Science teacher mode on) -snip-

It just so happens that my fourth-grade science fair experiment was entitled 'The Effect of Weight on Speed'!

The entire experiment consisted of me rolling a little Lego car down a slope three time while timing it, and then doing the same thing - but with twenty nickels in the bed. The heavier car started off slower, but it was actually going faster than the car without the nickels in it. The car without nickels hit its top speed faster, but it was slower overall.

[Tiberion]

Yeah lets not confuse the guy too early with terminal velocity

[RC1062]

Nobody has. That was David R. Scott, mission commander of Apollo 15, not Neil Armstrong (he commanded Apollo 11).

That was also my first thought...

[SmiteZero]

Of course you\'re correct. Point still stands.

[TNTGODZZ]

Yeah lets not confuse the guy too early with terminal velocity

aww we were just getting started