Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Physics Project help! What relationships should there be?

  1. Mar 10, 2012 #1
    I am currently doing a senior physics experiment where we are stopping a computer fan (with steel glued on to the blades) with an electromagnet, and measuring the time it takes to stop at varied resistances (using a rheostat).

    I also need to calculate the angular and linear momentum and torque (and possibly other things). I am confused about what relationship should form between the time the fan takes to stop and the resistance - as well as how to go about collecting enough data to calculate the other things (momentum etc.)

    Any help/advice/suggestions would be MUCH APPRECIATED!

    Thanks in advance.
  2. jcsd
  3. Mar 10, 2012 #2


    User Avatar
    Gold Member

    Why do you think linear momentum is going to be significant here? Doesn't everything move in a circle?

    You need to think about the mechanics of your experiment, make a mathematical model of it, and write the resulting equations. Sounds like you have not done this yet. Give it a shot and see what you come up with before asking for too much help.
  4. Mar 10, 2012 #3
    I'm not sure about linear momentum - my teacher told me to include it. Thanks for your reply, but I don't understand what you mean by a mathematical model. Sorry, I must seem very thick - but we haven't been taught much of the theory and the info on the internet is quite confusing for the beginner! Could you start me off?

    Any of your help is very much appreciated.

    Thank you!
  5. Mar 11, 2012 #4


    User Avatar
    Gold Member

    A mathematical model is simply a system of equations that describe what is happening in your system. They may, or may not be solvable, but they are still your best effort to descibe the system operation.
  6. Mar 27, 2012 #5
    No, not at all. Physics is a hard subject to grasp and we are here to help.
    Start off with the mathematical model, and we'll see what you come up with.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook