# B Advice For My Physics Experiment

1. May 13, 2017

### zeldaspurpose

So for my curriculum I have to do a physics experiment and write a 2000 word essay on it. For my experiment, I'm planning to wrap a string with a ball attached to it n number of times around a pole and measure the time taken for it to unwind by changing variables such as the radius of the pole, the length of the string, the mass of the ball, the angle etc. I suggested this to my teacher and he said "Go ahead, but you have to figure out a way to control the force pulling, then you'll be fine." What does he mean by the force pulling? Also, how any suggestions on how I should control it?

2. May 13, 2017

### sophiecentaur

PF tries not to hand people solutions on a plate so I will ask you what you actually had in mind to do in the experiment. How do you intend to provide the force and how do you intend to measure / "control" it? A diagram would enable us to discuss your ideas. Have you already drawn a diagram? If not, then you really should.

3. May 13, 2017

### Staff: Mentor

I assume he means the tension in the string.

4. May 13, 2017

### andrevdh

I think your teacher means "controlling" gravity, that is changing the force pulling the ball downwards.

5. May 13, 2017

### Staff: Mentor

Hmmm. Well, the obvious solution is to ask the instructor since this seems to be more of an issue with understanding the instructions and less with how to accomplish them.

6. May 13, 2017

### sophiecentaur

That's always my reaction to this sort of question but I know that some teachers can be reluctant to get involved. Often it's because they are presenting ideas from somewhere / someone else and haven't really thought the proposed experiment through. Consequently it's a real drag when a student turns up and challenges them.
I did have similar problems at University, getting access to the right sort of help (particularly when I was late getting into a project - mea culpa)
Now we have an INTERNET, available to all, it is always worth while spend a long time searching for descriptions of similar experiments because a popular experiment will always have been written up and published somewhere. That skill is the very first one that students should learn but they need to be self motivated and self taught.

7. May 13, 2017

### Staff: Mentor

If a student is unsure of what you're even asking them to do, I can't imagine why you wouldn't clarify for them. This reminds me of my weekly lab session. I swear we spend a quarter of the time or more just trying to figure out what the instructions are asking us to do...

8. May 13, 2017

### sophiecentaur

It's a pretty common problem for students. And it does take some nerve to march up and ask if you think you should actually know. Personally, I was always so interested in how they would do their practicals that I would get what was probably too involved and enthusiastic. That can wind 'em up too!

9. May 14, 2017

### Tom.G

Is there a misunderstanding as to orientation?

pole
pōl/
noun
noun: pole; plural noun: poles
1
.
a long, slender, rounded piece of wood or metal, typically used with one end placed in the ground as a support for something.
"a tent pole"

10. May 15, 2017

### sophiecentaur

The operative word is "typically". Many tents have horizontal ridge poles.
Quoting from dictionaries is seldom much use in a technical argument with people who's first language cannot be relied on to be the same version of English as ones own (that can include Engineers and engineering terms too).

11. May 15, 2017

### andrevdh

the "obvious" way to control the pulling force is to alter the mass of the hanger (without changing its size or shape)

12. May 15, 2017

### sophiecentaur

@zeldaspurpose
You have not replied to the thread. Have you been frightened off by the mass of responses? No need to be. We don't bite but we do tend to be very enthusiastic!

13. May 15, 2017

### Tom.G

Yup. Just trying to clear up an ambiguity.
The Op in the original post said:
That brought to mind a Tether Ball configuration, i.e. a vertical pole with a tethered ball attached to the top and school kids competing as to which way the tether could be wrapped around the pole.

Since all other responders assumed a horizontal pole, it seemed an appropriate question.

14. May 17, 2017

### andrevdh

that is what I also thought (from the start) a vertical pole