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

Homework Help: Air Resistance Lab Help (Logs)

  1. Nov 9, 2004 #1
    In this lab we dropped coffee filters from a given height (3 M) and want to determine their terminal velocity

    My problem is I don't know how to solve the log thing given.


    we have terminal velocity, V, in the formula

    Mg = bV^n which I change to V=(Mg/b)^(1/n)

    then to solve this I go

    ln V = (1/n)[ln(M) + ln(g) - ln(b)]

    I know the Mass, I have an average velocity I can substitute in for V and g, as usual, is 9.81 m/s^2

    b is a constant dependent on the shape of the object, or "shape factor" and n is the power of the velocity (which I am guessing should come out somewhere close to 2, although assumptions are always bad)


    when i go n = [ln(M) + ln(g) - ln(b)]/[ln (V)] everything comes out crazy and makes no sense

    my physics teacher told me to disregard all laws of logs and just go [ln(M) + ln(g) - ln(b) - ln (V)]


    when I put it in my calculator and solve simultaneously it comes out and the numbers make sense, but I have no idea what my calculator is doing to get those answers.
     
  2. jcsd
  3. Nov 9, 2004 #2
    What exactly are you trying to solve for? n?

    What values are already known?

    --J
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook