# Physics resit soon! help ! a VERY simple graph problem

1. Apr 6, 2009

### tommyleehutch

physics resit soon! help plz! a VERY simple graph problem

This is physics from the last year of highschool. So think of me as being about 17ish or 18ish.

The exam/test thing is for uncertainty. It will involve graphs.

I have to express one thing from a graph in terms of another involving the gradient.
One of the two quantities will be squared or rooted or 1/x or 1/x^2.

question 1 (the important one!)

This here is an answer ( I don't have the question ).
I'm sure the question would have read something like:
"show the link between frequency and time period"
F^2= (43 +- 3) T
(or)
f = (6.6 +- 0.3) sqroot T

43 and 6.6 are the gradients. 3 and 0.3 are the uncertainties. (note that 0.3 was rounded from 0.23)
Only one of those is needed its just when you graph the data in the exam you have the choice of how to graph it.
One is from a F^2 against T graph and the other from a F against sqroot T graph.
I'm guessing the answer from above must be about a pendulum or something. lol

My problem is I don't know which way to graph it.
For example if I got that exact question tommorrow what is to stop me from expressing the answer as T = (43 +- 3)f^2 [as opposed to the correct answer F^2= (43 +- 3) T]
???
thats the thing for me.
I don't know if the axis is important?
I'm guessing it is, but actually I don't remember the question so I don't know which quantity was y axis and which one was x axis. So I can't even check that to tell you....

anyway that there is alot of info, perhaps even too much, plz post and let me know if something needs clarify. I'm more than happy to. :D!

I really need that but also I have 2 more questions related to my exam.

rounding: if i get uncertainty (absolute) for example 55.5 +- 1.32456787654345678
and i want to round it... should it become 55.5 +- 1.3 or 55.5 +- 1.4
you could round it down just like you normall would do when rounding.
however you might want to round it up to increase its uncertainty.
hmm?

time's axis: I heard that independent on x and dependent on y.
However there is exception that if time is involved it always go on x.
However I'm just wondering is there an exception that could actually have time placed on the y axis???

2. Apr 6, 2009

### kbaumen

Re: physics resit soon! help plz! a VERY simple graph problem

About graphing, think of it like this: Put the independent measure on x-axis and the one that depends on it on y-axis. Time always goes on x-axis because all the processes that involve time, are time-dependent. Can you think of anything on which time is dependent? I don't think so.

For example, if you have an object moving with constant acceleration, than it's velocity is time-dependent. If you wanted to graph it's velocity equation, than time would go on x-axis and velocity on y-axis, where from the graph we can see that the more time has passed, the more the velocity has increased.