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: Car turning round

  1. Dec 16, 2004 #1
    A car is turing round a bend of radius 100m and banking angle 15 degrees. If the coefficient of static friction between the tyres and the road is 0.1, determine the range of speeds within which the car can turn safely round the bend.

    Here is what I have done:

    [tex] R sin \theta + f >= \frac{mv^2}{r} [/tex]
    [tex] R sin \theta + \mu R >= \frac{mv^2}{r} [/tex]
    [tex] R (sin \theta + \mu) >= \frac{mv^2}{r} [/tex]
    [tex] mg cos \theta ( sin \theta + \mu) >= \frac{mv^2}{r} [/tex]
    [tex] v<= \sqrt{rgcos\thata (sin\theta +\mu)} [/tex]
    [tex] v<= 18.6 ms^{-1} [/tex]

    I don't know how to find the other one range, and the answer is 12.7 < v< 19.6....I am confused...please help.. :confused:
  2. jcsd
  3. Dec 16, 2004 #2

    Doc Al

    User Avatar

    Staff: Mentor

    To solve this problem, do this:

    First identify all the forces acting on the car. I see three forces: weight, normal force (perhaps that's what you call R), and friction.

    Now apply Newton's 2nd law: The net horizontal force on the car will produce the centripetal acceleration, while the net vertical force will be zero.

    The range of speeds is obtained by realizing that at one extreme the friction points down the incline, while at the other it points up the incline.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook