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: Banked Curves

  1. Apr 6, 2008 #1
    1. The problem statement, all variables and given/known data
    A circular highway curve with a radius of 200m is banked at an angle such that a car traveling 45km/h can just make it around the curve if the highway surface is frictionless.
    a. what is the angle between the highway surface and the horizontal?
    b. if a car travels at 40km/h around the curve, what is the centripetal force acting on the car?
    c. What is the minimum value of the coefficient of friction between the tires and the highway surface necessary to prevent the car in (b) from skidding?
    d. If the angle of the highway curve is as in (a), but the radius of the curve is increased to 300m, what is the speed a car must be going in order to negotiate a curve without skidding?

    2. Relevant equations
    tan(theta) = v^2/gr

    3. The attempt at a solution
    45km/h would be 12.5m/s
    a. tan(theta) = (12.5m/s)^2 / 9.8*200
    theta = 4.6degrees
    b. I know that F_n sin(theta) = mv^2/r
    but I'm confused how to solve this one.
    c. I'll leave this blank since I haven't solved (b)
    d. sqrt{tan(4.6)(9.8)(300)} = v = 15.4m/s correct?
    Last edited: Apr 6, 2008
  2. jcsd
  3. Apr 6, 2008 #2
    For part C, I have F_f = u_s F_n
    v^2 = u_s gr
    1600 = u_s(9.8)(200)
    u_s = 0.816 right?

    For part D, I have sqrt(tan(4.5)(9.8)(300)) = v = 15.2 m/s is that right?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook