Mythbusters plan to uncover plane on conveyor belt - Page 51

Texaggie7nine

6:19p, 1/31/08

quote:
It is not possbile for the plane's speed to be relative to the conveyor belt's speed.

If you draw a dot on the belt. You can measure the speed at which the plane is moving away from that dot. This is why I have been saying the speed in relation to the belt's direction.

Red Skye

6:26p, 1/31/08

OK, let me rephrase this one last time. You're right, there is a relative speed of the plane to the conveyor belt. But this has, except for a completely negligable amount of friction, absolutely no effect on the speed of the plane relative to the ground.

TexasRebel

6:32p, 1/31/08

unless the conveyor is traveling at 6 lyps

but then you get into the whole time travel thing...

Red Skye

6:33p, 1/31/08

Thus my disclaimer, Rebel.

[This message has been edited by Red Skye (edited 1/31/2008 6:34p).]

jokershady

6:34p, 1/31/08

jesus tap-dancing christ!

let this thread die already!

Red Skye

6:35p, 1/31/08

We're more than halfway to 100. We can't let it die now.

jokershady

6:36p, 1/31/08

Red Skye

6:37p, 1/31/08

TexasRebel

6:38p, 1/31/08

the saddest part is:

videoag98 reneged on his promise to quit at 200,000 views on the original thread...

well...who's attempting to quit this time?

not it!

Red Skye

6:42p, 1/31/08

I'm in it for the long haul.

Texaggie7nine

6:47p, 1/31/08

quote:
But this has, except for a completely negligable amount of friction, absolutely no effect on the speed of the plane relative to the ground.

I'm not arguing that it does. I'm arguing that the wording makes a world of difference.

If the plane is traveling away from the direction of the belt at the same speed the belt is moving, then the plane is stationary. Forget the logistics of how it is that way, we are talking about the actual statement.

[This message has been edited by Texaggie7nine (edited 1/31/2008 6:48p).]

Red Skye

7:14p, 1/31/08

quote:
If the plane is traveling away from the direction of the belt at the same speed the belt is moving, then the plane is stationary. Forget the logistics of how it is that way, we are talking about the actual statement.

No it's not stationary. The plane will never be stationary. It is impossible for the plane to be stationary, no matter how you word the problem.

kraut

7:28p, 1/31/08

http://www.youtube.com/watch?v=siYQU99VaAM

Free body diagram.

91_Aggie

7:30p, 1/31/08

quote:
If the plane is traveling away from the direction of the belt at the same speed the belt is moving, then the plane is stationary. Forget the logistics of how it is that way, we are talking about the actual statement.

Wow! I can see someone getting caught on the semantics of the way the problem was worded, but to still believe the above at this point is ludicrous.

If you can't understand that the speed of the conveyor belt has no real effect on the plane's ability to move forward then I don't know what can be done to convince you.

fahraint

8:01p, 1/31/08

What if the plane had no wheels, and was nothing but a big heavy block of wood?

Ag with kids

8:17p, 1/31/08

quote:
Unless it can generate enough thrust to go ballistic, but even that is flawed since the engines would have to be facing up.

The plane I spent this afternoon working on could take off from the conveyor belt easily...since it CAN point the engines up...

Until it wants to go fast and then points the engines forward...

I got my HQ engineer's stomach all queasy, too...

Ag with kids

8:17p, 1/31/08

quote:

What if the plane had no wheels, and was nothing but a big heavy block of wood?

It would have the flying qualities of an F-4 with both engines out????/

OneManArmy

8:24p, 1/31/08

quote:
If the plane is traveling away from the direction of the belt at the same speed the belt is moving, then the plane is stationary. Forget the logistics of how it is that way, we are talking about the actual statement.

If you look at it this way you are assuming that the plane is only providing enough forward thrust with its engine to counteract the rolling friction of the wheels. That is a pretty stupid assumption.

Yesterday

8:31p, 1/31/08

fahraint

8:31p, 1/31/08

quote:
It would have the flying qualities of an F-4 with both engines out????/

What if it fired its missles backwards?

Texaggie7nine

8:36p, 1/31/08

quote:
If you can't understand that the speed of the conveyor belt has no real effect on the plane's ability to move forward then I don't know what can be done to convince you

When the F did I ever say that it did? I am saying that by the wording of the statement the plane is stationary if it is going the same speed away from the belt movement as the belt is traveling.

Red Skye

8:38p, 1/31/08

No, it's not.

fahraint

8:38p, 1/31/08

the wheels may be going the speed of the conveyor, but the plane moves forward, the conveyor goes faster, the wheels go faster, the plane moves forward....ad infinatum, then the plane takes off

coconutED

8:41p, 1/31/08

quote:
I am saying that by the wording of the statement the plane is stationary if it is going the same speed away from the belt movement as the belt is traveling.

And we are saying that this is impossible. It can never happen. Not in theory. Not in practice. NEVER!

Imposing such a condition on the problem makes it unsolvable. In engineering, we refer to this as over specifying your initial conditions.

Ag with kids

8:46p, 1/31/08

quote:
What if it fired its missles backwards?

If the missiles had a coconut on a string between them then it's possible...

OneManArmy

8:46p, 1/31/08

By giving the belt a speed you are giving a speed relative to a stationary point (the ground). For the problem to make sense one would naturally assume that the plane's speed is also relative to the ground because that is the assumed point of reference for everything.

Now....

fahraint

8:48p, 1/31/08

quote:
then it's possible

Ag with kids

9:04p, 1/31/08

ONLY with the coconut on a string, mind you...

fahraint

9:06p, 1/31/08

quote:
then it's possible

what if the block of wood airplane was glued to the conveyor, and fired its missiles backwards?

[This message has been edited by fahraint (edited 1/31/2008 9:20p).]

Rex Racer

9:26p, 1/31/08

This thread reminds me of a discussion that I once had with howdydamnit04.

http://www.texags.com/main/forum.reply.asp?forum_id=12&topic_id=507647

Ag with kids

9:44p, 1/31/08

quote:
what if the block of wood airplane was glued to the conveyor, and fired its missiles backwards?

As long as the missiles had the coconut on the string, it would take off...

If it was glued down, it would just take that damn conveyor for a ride...it needed to get out anyways....

fahraint

9:47p, 1/31/08

what if the coconut had no milk inside, because it was previously drained on Survivor?

Ag with kids

10:16p, 1/31/08

Then drop the conveyor down on that Survivor choad because he ruined the experiment!!!!

Texaggie7nine

11:03p, 1/31/08

quote:
And we are saying that this is impossible. It can never happen. Not in theory. Not in practice. NEVER!

I already explained earlier how it could be accomplished in practice for a moment. You just have a problem dealing with the theoretical. You can't say, well it's impossible so we will say the wording of the myth can mean only one thing.

Texaggie7nine

11:06p, 1/31/08

quote:
that the plane's speed is also relative to the ground because that is the assumed point of reference for everything.

That's pointless, because then, if the plane is going 25 mph forward, relative to the ground, then it is going 25 mph relative to the ground and it takes off. So why even pose the question of the myth.

Basically the myth should be cut off at "the plane is moving forward at takeoff speed, relative to the ground" and that would be end of story. You can say anything after that but it would not negate that you stated that the plane is going at takeoff speed relative to the ground.