# B How should I express this angle in words?

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1. Dec 4, 2017

### ChanYoung Park

Hi! The diagram above is showing a man swinging a swing (a facility you can find in playgrounds) back and forth. I'm trying to come up with a concise expression in words that describes the angle noted as theta so that I can write a clear and effective research question (theta is the independent variable in my research). How should I express this angle in words (or in English)??

2. Dec 4, 2017

### NickTheFill

My attempt...
Where theta is the displacement angle of the swing from equilibrium.

3. Dec 4, 2017

### FactChecker

With positive angles in the forward direction.

4. Dec 4, 2017

### Nidum

--- relative to the vertical . You must always provide a datum zero for any position variable in mechanics .

5. Dec 4, 2017

### ChanYoung Park

So will it be
"Displacement angle of swing from equilibrium relative to the vertical with positive angles in the forward direction"....?

6. Dec 4, 2017

### sophiecentaur

I would have thought that a diagram with the displacement angle and the restoring force marked would be quite good enough. It is a very standard set up and not likely to be to be misunderstood. Maths is often better than words to describe such things. No need to worry overmuch. I think.

7. Dec 4, 2017

### FactChecker

Even with full use of mathematics, a careful and precise definition of the variables and coordinate systems is a good practice.

8. Dec 4, 2017

### ChanYoung Park

The problem is that I will get marks for my research question and it will be marked based on how clear the dependent and indenpendent variables are; it's mentioned in the criteria...

9. Dec 4, 2017

### FactChecker

Then you want a diagram and the correct word descriptions. The diagram helps very much to visualize but I have seen many diagrams that get too complicated to really be clear about each part. Therefore, clear word definitions are also nice.

Last edited: Dec 5, 2017
10. Dec 5, 2017

### Delta²

Can't we simply call it "inclination angle" or "polar angle"???. Isn't it so if we choose a spherical coordinate system with its origin at the hinge? (and proper directions for positive orientation).