Lab Report Graph Question

[ElLos]

I need someone to explain this to me:

In a time-displacement graph,

Why is time the independent variable?

I need this for a Uniformly Accelerated Motion experiment.

Also, does someone know how to find the maximum and minimum gradient in a graph?

[Slovakov]

If ypu put time as a dependent variable, you would measure the change of time in a given displacement, and this is not what you want to get because the vaue of time increases independently of the motion of an object. Moreover , in some cases such a graph wouldn't even be a function, because it is possible that for two different values of time there is the same value of displacement (this won't happen in case of uniformly accelerated motion).

As for the max and min gradients: you should draw the steepest and the least steep graph that would still pass through all the error bars, and then calculate their gradients. Unfortunately, I don't know the software that would do it for you and you'd probable have to do it on paper (anybody knows such software?).

[dessskris]

Logically time cannot be dependent... The displacement depends on the time, not the other way round.

You need to do it manually. I personally use Excel, but it's very complicated. If you are not familiar with Excel formulas, you will go through hell and back just to learn it. I have a guide here though for VIPs to look over.

Or if you use a graphing software, what you can do is:

For example the coordinates of the points at both ends of the curve are (2.5, 3) and (10, 8.5) where (x, y) are (time, displacement).

The uncertainty of the displacement is 0.2 units.

Maximum line: (2.5, 2.8) and (10, 8.7)

Minimum line: (2.5, 3.2) and (10, 8.3)

Plot the 4 points on the same axes with the original graph and connect each pair.