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

Maximum power when torque is 0 and angular velocity is 0

  1. Oct 5, 2011 #1
    1. The problem statement, all variables and given/known data

    What is the power the drill can supply at the two points of interest(The intersections at the axis')

    This is a direct translation of the dutch problem. So basically what's going on is we made measurements of the RPM and angular displacement of our mechanical system (irrelevant at this point) We then converted all the points (correctly) into angular velocity (the RPM points) and the angular displacement to axial torque applied. We then used a scatter plot to plot these points (as per instruction) and found an equation for the linear regression (all using MATLAB)

    So it boils down to the fact that I have an equation like this:
    y= 0.15781x + 155.11

    Where y is axial torque as a function of angular velocity.

    So to come back to my first point; they are asking for the power at the axis intersections so when there is no moment opposing the motor (maximum angular velocity) and when there is no angular velocity (so maximum moment -> drill stationary)

    But how can this even be right? The equation for power is P = T*ω

    So when either one is zero the answer is zero but this can't be right can it?

    I hope I have explain it thoroughly enough...
  2. jcsd
  3. Oct 6, 2011 #2
  4. Oct 6, 2011 #3


    User Avatar

    Staff: Mentor

    when w is close to zero, T will be high since P is roughly constant.
  5. Oct 6, 2011 #4
    Yes but the problem states we have to find the power at both T and w when they are close to 0. How should I got about doing this? This (first post) is all the information available
  6. Oct 6, 2011 #5


    User Avatar

    Staff: Mentor

    Ignore my earlier post; I wasn't paying attention.

    y= 0.15781x + 155.11

    When x=0, you can calculate the maximum torque. Since it's not turning, it's doing no work, and because power is rate of doing work, so power=0. :smile:
  7. Oct 6, 2011 #6
    That's what I thought but it can't be THAT easy can it? But I guess it's some sort of a trick question because there are no maxima in a linear equation (which we were supposed to find) so 0 it is!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook