Planetarion Forums

Ragnarak · 16 Oct 2003, 20:00

Ok, you're in an airplane flying a parabolic path. You experience weightlessness during the flight but it's not during the whole of the parabolic part of the flight is it?

It's just during part of the peak? How do i work out how long the weightlessness lasts for?

I got the feeling i'm missing something very simple.

heh.

MrL_JaKiri · 16 Oct 2003, 20:02

It depends.

I could make a lengthy post, but it's dindins time.

Ragnarak · 16 Oct 2003, 20:03

Quote:

Originally Posted by MrL_JaKiri

It depends.

I could make a lengthy post, but it's dindins time.

I was counting on the lengthy post from you

cnaw · 16 Oct 2003, 20:03

Quote:

Originally Posted by Ragnarak

Ok, you're in an airplane flying a parabolic path. You experience weightlessness during the flight but it's not during the whole of the parabolic part of the flight is it?

It's just during part of the peak? How do i work out how long the weightlessness lasts for?

I got the feeling i'm missing something very simple.

heh.

this won't help, but i wanted to link to somthing that listed the vomit comet

ChubbyChecker · 16 Oct 2003, 20:07

Quote:

Originally Posted by Ragnarak

Ok, you're in an airplane flying a parabolic path. You experience weightlessness during the flight but it's not during the whole of the parabolic part of the flight is it?

It's just during part of the peak? How do i work out how long the weightlessness lasts for?

I got the feeling i'm missing something very simple.

heh.

If I understand your question correctly (which I probably don't) then the only time you feel weightless is during free-fall. ie when the plane is flying downwards, very fast.

MrL_JaKiri · 16 Oct 2003, 20:07

Quote:

Originally Posted by Ragnarak

I was counting on the lengthy post from you

It depends on the type of weightlessness.

There is instantaneously weightlessness at the top (the kind you get when a lift starts going down quickly), but the more proper kind comes if the plane is in freefall, with no lift being generated and very little frictional effects. Then there is no reaction force from the plane when you stand on it (because you're accelerating at the same rates), so it feels like you're weightless.

[edit]

Although only the latter one really applies in this case, because the transition in the parabola will probably be too shallow. The former really only applies in sharp changes of direction.

Dace · 16 Oct 2003, 20:07

It's on the way down you 'feel' weightless.

Intrepid00 · 16 Oct 2003, 20:10

Weightlessness feeling is when you have reached terminal velocity I thought when going down and at the very peak before a decent after travling upwards fast. None of them are weightlessness just a feeling of what its like due to some physic laws.

Cyp · 16 Oct 2003, 20:11

At the point when d²t/dg²=s, where t is the position of the plane, g is the time and s is the force on the plane by gravity.

Ragnarak · 16 Oct 2003, 20:11

Quote:

Originally Posted by MrL_JaKiri

It depends on the type of weightlessness.

There is instantaneously weightlessness at the top (the kind you get when a lift starts going down quickly), but the more proper kind comes if the plane is in freefall, with no lift being generated and very little frictional effects. Then there is no reaction force from the plane when you stand on it (because you're accelerating at the same rates), so it feels like you're weightless.

[edit]

Although only the latter one really applies in this case, because the transition in the parabola will probably be too shallow. The former really only applies in sharp changes of direction.

Cheer, just wanted to make sure i wasn't misunderstanding something simple.

MrL_JaKiri · 16 Oct 2003, 20:13

Quote:

Originally Posted by Intrepid00

Weightlessness feeling is when you have reached terminal velocity I thought when going down and at the very peak before a decent after travling upwards fast. None of them are weightlessness just a feeling of what its like due to some physic laws.

They're equivilent.

Ragnarak · 16 Oct 2003, 20:21

One last bit.

I'm right in thinking that a 45 degree angle would lead to the maximum time of flight right?

Then why do the use steeper angles like 50 degrees?

MrL_JaKiri · 16 Oct 2003, 20:27

45 degree angle = best is only true in that model.

You've got to factor in:

Lift.

Air Resistance.

Lift at various angles of attack

Air Resistance at various angles of attack

etc

XeeThot · 16 Oct 2003, 20:28

The feel of weightless is given by being in a confined space that is falling at the same speed than you. Everything inside it 'becomes' weightless and as you don't see the outside you can't tell everything is in fact falling.

The reason for the 50 degree angle must be related with air resistance decelerating the plane or simply to make it safer for the pilot to pull up.

Ragnarak · 16 Oct 2003, 20:29

Quote:

Originally Posted by MrL_JaKiri

45 degree angle = best is only true in that model.

You've got to factor in:

Lift.

Air Resistance.

Lift at various angles of attack

Air Resistance at various angles of attack

etc

doh of course

i've been doing fairly complicated stuff recently and now gone back to what's basically a-level and forgot half of it