Variables in a lab (controlled, independant and dependant)

[Simon George]

Hi!
So it's new for me to do physics lab that way and my teacher is asking us to define the independent, independent and controlled variables of every lab we're doing. I'm not quite sure what they refer to... For example, in a moment of inertia lab (see picture), I am asked this question. The objective of this experiment is to experimentally find the moment of inertia of this system with a sensor that will measure the angular velocity. This is what I tried:

controlled variable: moment of inertia of the disk and ring
independent variable: the mass of the hanging mass
independent varable: the angular velocity

I have no idea if that is good as it is my first time doing this. Please ask below if you have any question about the experiment! thanks:)

 

[haruspex]

controlled variable: moment of inertia of the disk and ring
independent variable: the mass of the hanging mass

I cannot tell from your description which way around those should be.
A control (or controlled) variable is just something that is constant throughout the a series of tests, and which is not of primary concern. E.g. here the moment of inertia of the pulley would fall into that category. There may be several.
An independent variable should normally be one you are varying deliberately through a series in order to establish a relationship with the dependent variable(s).
If this was just a one-off measurement, I would guess you should make that the parameter to be computed, i.e. the moment of inertia of the ring. (On the princiole that on another such experiment you would use a different ring.)

 

[Simon George]

I cannot tell from your description which way around those should be.
A control (or controlled) variable is just something that is constant throughout the a series of tests, and which is not of primary concern. E.g. here the moment of inertia of the pulley would fall into that category. There may be several.
An independent variable should normally be one you are varying deliberately through a series in order to establish a relationship with the dependent variable(s).
If this was just a one-off measurement, I would guess you should make that the parameter to be computed, i.e. the moment of inertia of the ring. (On the princiole that on another such experiment you would use a different ring.)

Thank you for your answer! It is much more clear in my head now. Since 50g were added in the hanging mass, I think you are right and that the controlled variable is the moment of inertia, the independent is the mass of the hanging mass but I am not sure for the dependent variable... since the mass in the hanging mass is influencing the angular velocity, should I say that the angular velocity AND the angular acceleration are the dependent variable?
Again, thanks for your clear explanation of the variable!

 

[haruspex]

the angular velocity AND the angular acceleration are the dependent variable?

That is right. There can be any number of dependent variables, but it is perhaps only necessary to list the ones directly measured.
In a more complicated lab there may be more than one independent variable too.