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: Drag of Car across frictionless surface.

  1. Oct 3, 2008 #1
    1. a 1400 kg car with a cross section of 1.8m wide and 1.46m high slides across a frictionless surface at 19 m/s.

    The question is how long does it take (in seconds) to get to 13 m/s?

    the 2nd part is how long it does it take to get to 10 m/s?

    2. D = .5(A)v^2 where A is the area of cross section

    and basic mechanics equation V = Vo + at

    3. The real problem lies in the fact that drag changes over the change in velocity. I tried solving for it initially by plugging in different velocities for the drag equation but it doesn't come out right.

    So far, there is a drag force going backwards and the momentum of the car going forwards. I'm so frustrated because i believe that im missing something very simple to solve this.
    Last edited: Oct 3, 2008
  2. jcsd
  3. Oct 3, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi Joseph! Welcome to PF! :smile:

    Hint: use good ol' Newton's second law (force = rate of change of momentum) to make an equation involving t v and v/dt. :wink:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook