think about this... - Page 29

LAGmaniac · #**281** 11-23-2005, 04:27 PM

[ QUOTE ]
[ QUOTE ]

However, the OP never states that the system is frictionless so theoretically, as the converyor belt speed approaches infinity, the friction of the wheels is no longer insignicant and can actually cancel out the finite amount of thrust from an airplane engine.

[/ QUOTE ] Pretty sure we will have had lift off by then [img]/images/graemlins/wink.gif[/img]

[/ QUOTE ]

But imagine that that there is friction in the system, as in real life. The conveyor belt starts moving backward and the pilot creeps in the engines just enough to keep the plane staionary. The conveyor belt keeps speeding up and the pilot occasionally nudges in the throttle a tad to hold position. If the conveyor belt could continue speeding up like this until it approached infinity, wouldn't the friction in the system from the wheels eventually become so great as to counter full forward thrust by the engines?

#**282** 11-23-2005, 04:28 PM

[ QUOTE ]
who said the plane has perfect bearings?

[/ QUOTE ]

The OPer did at some point. You don't need perfect bearings either. You lose. Sorrry about the 4 bills.

jba · #**283** 11-23-2005, 04:28 PM

[ QUOTE ]
Respond to this post if you understand 2 things:

the plane will take off if the runway speed is fixed.

the plane will not take off if the runway speed is always the same as the tangential speed of the planes wheels.

[/ QUOTE ]

all right dude I'm coming around to your way of thinking.

let's stop wasting our time in this thread, I have an idea

let's create a system like this one, only the runway will roll FORWARD and the wheels will spin backwards at the exact same velocity. this way we don't need any engines to take off.

Slow Play Ray · #**284** 11-23-2005, 04:29 PM

[ QUOTE ]
[ QUOTE ]
thats the whole point of a treadmill, so you can run WITHOUT MOVING.

[/ QUOTE ]
Now throw rollerskates on and use the handles to pull yourself forward.

[/ QUOTE ]

I'm going to expand on this a little. Imagine you're on the treadmill, on roller skates with perfect bearings. Someone is controlling the speed of the treadmill for you, and they keep turning it up. Since you're on frictionless wheels, the speed of the treadmill doesn't affect you, right? Okay, grab hold of the handles now. Imagine that the dude keeps cranking up the speed on the treadmill. Is there any speed he could possibly turn it up to that could stop you from simply pulling yourself forward with the handles, with very little effort, if you wanted to?

goofball · #**285** 11-23-2005, 04:32 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
thats the whole point of a treadmill, so you can run WITHOUT MOVING.

[/ QUOTE ]
Now throw rollerskates on and use the handles to pull yourself forward.

[/ QUOTE ]

I'm going to expand on this a little. Imagine you're on the treadmill, on roller skates with perfect bearings. Someone is controlling the speed of the treadmill for you, and they keep turning it up. Since you're on frictionless wheels, the speed of the treadmill doesn't affect you, right? Okay, grab hold of the handles now. Imagine that the dude keeps cranking up the speed on the treadmill. Is there any speed he could possibly turn it up to that could stop you from simply pulling yourself forward with the handles if you wanted to?

[/ QUOTE ]

No, but then the rotational speed of your wheels woudl be faster than that of the treadmill.

#**286** 11-23-2005, 04:32 PM

[ QUOTE ]
[ QUOTE ]
How can a CPA understand this (thanks to Patrick [img]/images/graemlins/smile.gif[/img] ) and engineering types can't [img]/images/graemlins/confused.gif[/img]

[/ QUOTE ]

to be fair, these guys really aren't "engineering types"

i think the "physics types" have an edge over the "engineering types", although patrick is sort of both.

[/ QUOTE ]

the physics types assume the bearings are frictionless, whereas the engineering types live in the real world and account for these types of things [img]/images/graemlins/tongue.gif[/img]

jba · #**287** 11-23-2005, 04:32 PM

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
thats the whole point of a treadmill, so you can run WITHOUT MOVING.

[/ QUOTE ]
Now throw rollerskates on and use the handles to pull yourself forward.

[/ QUOTE ]

I'm going to expand on this a little. Imagine you're on the treadmill, on roller skates with perfect bearings. Someone is controlling the speed of the treadmill for you, and they keep turning it up. Since you're on frictionless wheels, the speed of the treadmill doesn't affect you, right? Okay, grab hold of the handles now. Imagine that the dude keeps cranking up the speed on the treadmill. Is there any speed he could possibly turn it up to that could stop you from simply pulling yourself forward with the handles if you wanted to?

[/ QUOTE ]

people are going to say

"but when you pull yourself forward, the wheels will be going faster than the treadmill" which is partially true

imagine instead of regular rollerblades with normal wheels, your POS rollerblades have cog wheels and the treadmill has, well, treads, so that when you pull yourself forward you are forcing the treadmill to speed up (while matching the velocity of your wheels)

lift off!!!

IndieMatty · #**288** 11-23-2005, 04:32 PM

Slow Play Ray · #**289** 11-23-2005, 04:33 PM

good call - clearly i suck at analogies.

Slow Play Ray · #**290** 11-23-2005, 04:34 PM

[ QUOTE ]
the physics types assume the bearings are frictionless, whereas the engineering types live in the real world and account for these types of things [img]/images/graemlins/tongue.gif[/img]

[/ QUOTE ]

i am the engineering type in every possible sense of the word, and this whole mess is my doing. [img]/images/graemlins/grin.gif[/img]