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 and velocity

  1. Jan 18, 2013 #1
    1. The problem statement, all variables and given/known data

    Given: effects of drag for a free falling body are a= 9.81[1-(v^2)*10^-4] m/s^2
    V0 = 0 m/s and the falling body is very very high

    Find: the velocity after 5 seconds and the bodies terminal velocity as t -> infinity

    2. Relevant equations

    ∫dv = ∫a dt

    3. The attempt at a solution

    ∫ 1/(1-(v^2)*10^(-4)) dv = ∫ 9.81 dt where t goes from 0 to 5

    When I integrate this I get

    5*10^(-4) * ln( abs( v+1) / abs( v -1)) - 5*10^(-4) * ln( abs(1) / abs( 1)) = 9.81 m/s^2 * 5s

    For some reason I don't think this is right and if it is how do you solve it?

  2. jcsd
  3. Jan 18, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    You have dv/dt = 9.81[1-(v^2)*10^-4].
    Can you rearrange that as t = ∫ f(v) dv?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook