What is the source of the normal force for a plane flying a loop-the-loop?

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Discussion Overview

The discussion revolves around the source of the normal force experienced by a plane flying a loop-the-loop. Participants explore the nature of forces acting on the plane and the pilot during this maneuver, comparing it to similar scenarios like rollercoasters.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question what the normal force is reacting to for a plane in a loop-the-loop, drawing parallels to rollercoasters where the normal force is due to the track.
  • One participant suggests that the normal force in the airplane scenario might relate to inertia, but expresses confusion about its direction at the top of the loop.
  • Another participant identifies the air as the source of the normal force, indicating that lift and gravity are the forces acting on the plane at the top of the loop.
  • It is noted that the normal force on the pilot is exerted by the seat, which is a different context from the rollercoaster example.
  • Some participants discuss the forces acting on the pilot, including weight and the force from the seat, which together provide the necessary centripetal force.
  • One participant emphasizes that the force felt by the pilot cannot solely be attributed to gravity, suggesting it is also due to the plane's interaction with the air.
  • There is a question raised about what exerts the force on the track in a rollercoaster scenario, with a response attributing it to the mass and inertia of the rollercoaster and the Earth.
  • A later reply discusses aerodynamic forces, suggesting that lift acts upward from the wings, but when the plane is upside down, the wings point down, complicating the understanding of the normal force.

Areas of Agreement / Disagreement

Participants express various viewpoints regarding the source and nature of the normal force in the context of a plane flying a loop-the-loop. There is no consensus, as different interpretations and models are presented without resolution.

Contextual Notes

Participants highlight the complexity of forces involved, including the roles of lift, gravity, and inertia. There are unresolved questions about the definitions and applications of normal force in different contexts.

metalmonkey
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Can anyone provide an explanation as to what the normal force is reacting to in the case when a jet is flying a loop-the-loop?? I understand for a rollercoaster that at the top of the loop the normal force is due to the track exerting a force back on to the rollercoaster cart, contributing to the centripetal force, but for a plane, where is the normal coming from?

Only thing I can imagine is that it has something to do with the inertia of the plane?? But then why would the normal act downwards at the top of the loop?

Cheers
 
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metalmonkey said:
Can anyone provide an explanation as to what the normal force is reacting to in the case when a jet is flying a loop-the-loop?? I understand for a rollercoaster that at the top of the loop the normal force is due to the track exerting a force back on to the rollercoaster cart, contributing to the centripetal force, but for a plane, where is the normal coming from?
The air.

AM
 
On the plane itself, consider the vertical forces acting at the top of the loop: The air pushing on the plane ("lift") and gravity. These forces must produce the (downward) centripetal acceleration of the plane if the plane executes circular motion.

The term "normal" force is usually reserved for the perpendicular force between two surfaces, such as between car and track in the roller coaster case. In the airplane example, one could ask for the normal force on the pilot (exerted by the plane) at the top of the loop.
 
look at it, as what's exerting the normal force on the person in the plane, which would be the chair.
 
Normal force

For the plane moving in a circle. If the magnitude of the velocity is constant, then by Newton's second law, the net force on the plane is towards the centre (centripetal force). The pilot in the plane (if tightly secured to the seat) will also move in a circle. At the top of the loop the weight acting on the pilot and force exerted by the seat on the pilot act downward. These two forces provide the size of the centripetal force.

n +mg = mv*v / r rearranging for n gives n = m(v*v /r - g)
 
mick5 said:
For the plane moving in a circle. If the magnitude of the velocity is constant, then by Newton's second law, the net force on the plane is towards the centre (centripetal force). The pilot in the plane (if tightly secured to the seat) will also move in a circle. At the top of the loop the weight acting on the pilot and force exerted by the seat on the pilot act downward. These two forces provide the size of the centripetal force.

n +mg = mv*v / r rearranging for n gives n = m(v*v /r - g)
And what is it that provides the force on the seat that the pilot feels. It can't be gravity. It is the force of the plane against the air.

AM
 
so if the track exerts a force on a car in loop to loop, what exerts the force on the track?
 
barney007 said:
so if the track exerts a force on a car in loop to loop, what exerts the force on the track?
The mass/inertia of the rest of the rollercoaster and the Earth to which it is attached.

AM
 
metalmonkey said:
Can anyone provide an explanation as to what the normal force is reacting to in the case when a jet is flying a loop-the-loop?? I understand for a rollercoaster that at the top of the loop the normal force is due to the track exerting a force back on to the rollercoaster cart, contributing to the centripetal force, but for a plane, where is the normal coming from?

Only thing I can imagine is that it has something to do with the inertia of the plane?? But then why would the normal act downwards at the top of the loop?

Cheers


The forces are the aerodynamic forces of lift which (usually) point up from
the wings. When the plane is upside down, the wings point down.

The easy way to visualize this is that there is a vacuum condition just above
the wings of plane which always pull the wings toward the vacuum.
 

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