How Does Air Speed Affect Aircraft Weight?

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Homework Help Overview

The discussion revolves around understanding the relationship between air speed and aircraft weight, specifically in the context of lift generated by air moving over an aircraft's wings. The problem involves calculating the weight of an aircraft based on given air density, wing surface area, and air speeds above and below the wings.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the concept of lift and its relationship to weight, questioning whether lift can be equated to weight in stable flight conditions.

Discussion Status

Some participants have provided clarifications regarding the equivalence of lift and weight during level flight, while others express uncertainty about their understanding of these concepts. The discussion is progressing with participants seeking to solidify their grasp of the underlying principles.

Contextual Notes

There is an assumption that the aircraft is in stable, level flight, which is critical to the discussion of lift and weight equivalence. The original poster expresses difficulty in connecting the concepts presented.

Mowgli
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Homework Statement



Air (density= 1.29 kg/m^3) passes over the top surface of an aircraft whoe effective wing surface area is 75.5 m^2 at a speed of 255 m/s. If the air speed beneath the wings is 135 /s, what is the weight of the plane.

Homework Equations



W=mg

The Attempt at a Solution



I know how to find the "lift" in Newtons due to Bernoulli's effect- but I am thrown off by this question. What is the weight? Please help!
 
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If you know how to find the lift in Newtons pushing upward on the plane, then ask what is the force of gravity in Newtons pulling the plane downwards? In stable flight these two are equal.
 
I'm sorry- I am not good at this. Are you saying the lift is the same as the weight?
 
Yes. Assuming that the airplane is in level flight and neither ascending nor descending, then the lift equals the weight. Just like when you are standing on the floor - the floor is pushing up on you with a force which exactly balances your weight. Otherwise you would be falling, since F=ma.
 
Right, that makes sense- thank you so much!
 

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