Uploaded December 2015 | Updated September 2026, 2 weeks ago
In this video, I explain how to obtain the equation for linear interpolation between two points. I then go through a simple example.
Linear interpolation can be useful when you need data at points where data does not exist. This happens a lot when looking at tabulated data. Here are some examples of tabulated data where linear interpolation can come in handy:
- Steam/vapor tables in thermodynamics
- Property tables in heat transfer
- Normal shock tables and isentropic relations tables in gas dynamics
In the video linked to below, I show you how to program this equation into a graphing calculator (TI-83), so you can use it on exams or whenever you need a quick estimate.
goo.gl/ntTuKl
In this video, I explain how to obtain the equation for linear interpolation between two points. I then go through a simple example.
Linear interpolation can be useful when you need data at points where data does not exist. This happens a lot when looking at tabulated data. Here are some examples of tabulated data where linear interpolation can come in handy:
- Steam/vapor tables in thermodynamics
- Property tables in heat transfer
- Normal shock tables and isentropic relations tables in gas dynamics
In the video linked to below, I show you how to program this equation into a graphing calculator (TI-83), so you can use it on exams or whenever you need a quick estimate.
goo.gl/ntTuKl

![Explained: Area-Mach Number Relation
Ever wonder why rocket nozzles have an hourglass shape, or why fighter jets use something called a converging-diverging nozzle? This video goes through one of the most fundamental concepts in compressible flow, and shows you why you need to first shrink down the area, and then expand the area to get supersonic flow.
NOTES
► When I talk about the choked flow, I didnt make it clear that you can increase the choked mass flow rate through the nozzle by increasing the stagnation pressure upstream of the nozzle. The mass flow rate will not increase only if you keep the same geometry and upstream stagnation conditions. That is, you cant increase the mass flow rate when the flow is choked by only decreasing the throat area and/or decreasing the back pressure.
► The flow will be sonic at the throat for isentropic flow (see the assumptions used in the derivation). This is not the case for real flows.
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→ 1D Mass Conservation
https://goo.gl/Wo8mcV
→ 1D Momentum Conservation
https://goo.gl/YJypbz
→ 1D Mass Conservation in Differential Form (Blog Post)
https://goo.gl/Q4ac2t
→ Speed of Sound
https://goo.gl/HPtH16
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REFERENCES
► Notes by Matt MacLean
► Modern Compressible Flow, Anderson
► Elements of Gasdynamics, Liepmann and Roshko
► Gas Dynamics, Zucrow and Hoffman
THUMBNAIL PHOTO CREDIT
By NASA [Public domain], via Wikimedia Commons Explained: Area-Mach Number Relation](https://i.ytimg.com/vi/DRjWdDxVtRM/mqdefault.jpg)


![Explained: Airfoil Chord [Airplanes]
The airfoil chord is a vital part of understanding the angle of attack of an airfoil, as well as other aerodynamic parameters in aircraft design. The definition of the chord line is straightforward, while the definition for the leading edge (LE)/trailing edge (TE) are a little more ambiguous.
Second of All Comment
The first of all comment (that I made in the video) was that the angle of attack actually changes based off of where you define the leading edge to be. The comment I forget to say in the video is that the chord length also changes based on the LE location. For the minimum x value LE, the chord line is longer than the minimum radius of curvature LE. Explained: Airfoil Chord [Airplanes]](https://i.ytimg.com/vi/Eh5W61iswSY/mqdefault.jpg)

![In a Nutshell: Afterburners
Lets talk about what afterburners are, when theyre used, and how they work. In my first In a Nutshell video, Im testing the waters on giving simplified explanations for complicated topics. Let me know what you think.
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→ Detailed Afterburner Video
https://goo.gl/nt9KBp
REFERENCES
► Afterburners in The Aerothermodynamics of Aircraft Gas Turbine Engines, Zukoski
► Mechanics and Thermodynamics of Propulsion, Hill and Peterson
► Aerothermodynamics of Gas Turbine and Rocket Propulsion, Oates
► Aircraft Propulsion, Farokhi
► Aerospace Propulsion Systems, Ward
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THUMBNAIL PHOTO CREDIT
By United States Navy, Mass Communications Specialist 2nd Class Michael D. Cole [Public domain], via Wikimedia Commons In a Nutshell: Afterburners](https://i.ytimg.com/vi/EuITkZPd5c4/mqdefault.jpg)


![Explained: Angle of Attack [Airplanes]
The angle of attack (AoA) is one of the most important parameters when studying how planes fly. By definition, it is the angle between some reference line of the plane (in our case the chord line of the wing) and the relative wind. The AoA will be vital when talking about lift curves and how wings generate lift.
Chord Line: http://www.youtube.com/watch?v=Eh5W61iswSY Explained: Angle of Attack [Airplanes]](https://i.ytimg.com/vi/Fm2Az-PgPUU/mqdefault.jpg)
