# What on Earth is a Vector force diagram, and how do I draw one?

Asked by After_dinner_trivia (156) December 2nd, 2013

I have been asked to “Construct a vector force diagram, showing the interaction of the forces acting on an aircraft in a steady turn”
However I have never come across a vector force diagram before, and all the information I found via Google is difficult for me to understand, would anyone mind dumbing it down for me and explaining how to go about completing my task?

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You know what speed is, right? It’s a certain distance covered within a certain time (let’s say in metres per second). So, if you’re travelling at 10 m/s, we know how fast you’re going, but we don’t know where you’re going. Speed is a scalar – it has magnitude, but no direction. A vector (as opposed to a scalar) has not just magnitude, but also direction. If you express your 10 m/s with an arrow for direction, it is no longer speed (a scalar), it is velocity (a vector).

Like velocity, force is a vector. It has not just magnitude, but also direction. The forces acting on your aircraft can be illustrated by drawing a diagram with arrows pointing in each direction toward which the forces are acting. For example, gravity is a force acting downward from the aircraft. So, draw an arrow downward to represent that force. There will be other forces acting on it as well – you’ll have to figure out what they are, and add them to your diagram.

Often, the arrows are drawn to (roughly) the scale of the magnitude of the forces. So, bigger forces get bigger arrows.

Does this make it a bit clearer? I’m actually surprised that you’ve been asked to draw one if you don’t know what it is. Is it for a class? If so, at what level?

That’s brilliant thanks! I’ve seen what you have described before, but I didn’t realise that it was a Vector force diagram, it’s just clicked now. It’s for a Level 3 Diploma in Aerospace, I missed a lesson a couple of days ago and I think that is when the Tutors covered the diagrams. Thanks a bunch @glacial.

You’re welcome. :)

glacial (12110)

Thank you for that wonderful explanation, @glacial! A couple of years late for me, but so well put.

@After_dinner_trivia Welcome to Fluther. Hope you’ll stay!

longgone (12099)

@After_dinner_trivia Here is a good example of one to give you an idea of what you should be drawing. The only thing I would do differently than the example above is label each vector with its force in Newtons as well as labeling the angle of the vector.

In engineering a vector force diagram is often called a Free Body Diagram or FBD as @uberbatman linked to. I’m sure you’ve figured it out by now since I’m a month late to this question but I’m studying aerospace too and I know how much it sucks to miss one lesson and getting stuck on the things that follow. Good luck with it all!

shrubbery (10155)

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