Physics Question

ordinaryjoe

ordinaryjoe

ordinaryjoe

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So the other day, I had a heated debate (an argument) with my physics teacher about a question in a paper we were doing, and want to see what you think.

Suppose that there is an aeroplane, which is tilted to the right side slightly. Ignoring air resistance, and all forces other than the lift of the wing and mavity, what path would the aeroplane follow?



Path 1 is half of a parabolic curve (y=|root x|) , whilst path 2 is a circle (evidently :p)

I shall say what way I argued later as to not make people bias.

Edit:
The plane is not increasing/decreasing in altitude
The lift in the plane obviously goes through the centre of mass
The only forces in play are the lift and mavity
The wings are the same and the lift is constant on both wings
The elevators exert no force on the plane
 
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How can we ignore air resistance yet keep lift? :p

Edit, it has to be path 2, the plane can't point perpendicular to it's direction of travel.
 
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Well you have to make some serious assmumptions about the aircraft not levelling off "automatically" and other stuff, but I'd go for the circular path.

You'd also lose some altitude as well, I think.
 
I know which way I think the plane would go - but struggling on how to explain why using terms of uplift & mavity. Hmm.

EDIT: being, I find it hard to imagine the parabola, assuming the jet engines are still doing their job at this point, and the plane hasn't banked further.
 
I was going to try and answer properly, with my limited physics understanding, but then I noticed this...

which is tilted
Click to expand...
It's not an aeroplane, it's a UFO. Tilt proves it.
 
I don't think either path is correct, if you think about it as just simple vector addition it would be a straight path at an angle to the engine thrust direction. A circle would require the use of elevators.
 
Well, all other things being equal, the resultant vector of acceleration will be towards the center of a circle. how much the plane is banked with determine the size of this circle.

But this is a really gross generalisation :p I mean it's only a circle if the engine's arent actually causing an acceleration in speed. If the magnitude of velocity remains the same then yes, it'll be a circle....Oh and it also assumes a specific magnitude of velocity which is going to be some function of the banking angle...
 
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You say it's tilted - is the rudder turned at all? 'cause otherwise that plane is just going to continue on in a straight line isn't it?
 
JRS said:
You say it's tilted - is the rudder turned at all? 'cause otherwise that plane is just going to continue on in a straight line isn't it?
Click to expand...

the question's looking at lift generated by the wings. That force produced by lift will point upwards 'with respect to the plane'. So when the plane is at an angle, the force will have an effect on the direction of the plane, redirecting it left or right depending on the bank.

EDIT: actually there's a lot more to it before we actually get to a turning motion so that's a good point....:confused:
 
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JRS said:
You say it's tilted - is the rudder turned at all? 'cause otherwise that plane is just going to continue on in a straight line isn't it?
Click to expand...

Nope... No tilt on the rudder... Just the plane

A few things to clear things up:

The plane is not increasing/decreasing in altitude
The lift in the plane obviously goes through the centre of mass
The only forces in play are the lift and mavity
The wings are the same and the lift is constant on both wings
 
Hmm, id say 2. However number 1 looks like it could either be a slow right hand turn, or a very long circle?

Im guessing you were going for a righ hand turn.
 
Firstly I think the question is too simply worded to b a decent question in the first place. there is no mention of whether level flight is being maintained or if thre is a tailplane etc.
so in the confines if the question i think that the plane will fly in a straight line diagonal to the direction the plane is facing.
assuming the speed of the plane is adjusted to maintain level flight and the only other forces are mavity and lift, the the lift from the wings acts perpendicular to the wing, ad hence at an angle to the ground.
so there is a vertical component to the lift and a horizontal component.
the vertical component is balanced with the weight of the plane (hence level flight) and the horizontal component is dragging the plane sideways, because there is nothing to resist it.
the plane is not turning because there is only one horizontal force acting on it (as explained in the badly worded question) and you need forces to make something turn
 
I would say it's neither of those and that it travels roughly in a NE direction (assuming top of the page is north and looking at the plane from above).
 
ordinaryjoe said:
Nope... No tilt on the rudder... Just the plane

A few things to clear things up:

The plane is not increasing/decreasing in altitude
The lift in the plane obviously goes through the centre of mass
The only forces in play are the lift and mavity
The wings are the same and the lift is constant on both wings
Click to expand...

What about the elevators?
 
ordinaryjoe said:
The only forces in play are the lift and mavity
Click to expand...

In that case, the plane can only move up and down. If we ignore air resistance the plane will therefore travel straight forwards at a constant velocity when viewed from above.

Can I just say you're putting some horrendous constraints on what we are and are not allowed to factor into the equation.
 
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