1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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?

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