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!

Uncertainty Problem

  1. Aug 30, 2004 #1
    Here's the problem:

    A magazine publishes lateral acceleration capability from cars it tests. Measurements are made using a 150' diameter skidpad, the vehicle path deviates from the circle +/- 2 ft and the vehicle speed is read from a fifth wheel sensor measuring the system to +/- .5 mph. Then it says to estimate the experimental uncertainty if the reported lateral acceleration is .7g.

    All I can think of is A=v^2/r...and some how i would have to cut the 150 diameter into 75 as a radius. I got 75 +/- .0133. then i found v = to 22.69, and you have to square that...I'm basically stumped...the answer is like 4.XX% :frown:
  2. jcsd
  3. Aug 31, 2004 #2
    I did the calculation and I got 8%.
  4. Aug 31, 2004 #3
    hmm well its supposedly like 4.45%, i have a feeling this has something to do with partial derivatives?
  5. Aug 31, 2004 #4
    no, you dont need partial derivatives to solve it. Ill get back to you with the answer, by the way, how many feet in a mile?
  6. Sep 1, 2004 #5
    5280 feet in mile
  7. Sep 1, 2004 #6
    I Still cant get it, I get something liek 3.8%.
  8. Sep 1, 2004 #7


    User Avatar
    Science Advisor
    Gold Member

    See if this helps
    [tex]A = \frac{1.226r}{t^2}[/tex]
    A = acceleration in g's
    r = radius of track
    t = time [in seconds] to complete 1 lap
    This is how g's are calculated on a skidpad
    re: http://www.carcraft.com/howto/53698/index7.html
  9. Sep 1, 2004 #8
    yeah but im not given any information about times
  10. Sep 2, 2004 #9


    User Avatar
    Science Advisor
    Gold Member

    try substitution. T = d/v. The equation then becomes
    [tex]A = \frac{1.226rv^2}{d^2}[/tex] Does that help?
    Given the uncertainty of measurements in the quantities r and v, the answer is there. I agree with the 4.xxx% result, see what you get.
    Last edited: Sep 2, 2004
  11. Sep 7, 2004 #10
    I'm still not following how to get that 4.45 answer, can you please elaborate for me?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Uncertainty Problem
  1. Uncertainty problem (Replies: 1)

  2. Uncertainty Problem (Replies: 6)