1. Not finding help here? Sign up for a free 30min 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!

2 Super Hard Rotational Motion Problems

  1. Dec 3, 2003 #1
    1.) A car rounds a banked curve where the radius of curvature for the road is R, the banking angle is 0(theta), and the coefficient of static friction is [mu]. (a) Determine the range of speeds the car can have without slipping up or down the road. (b) What is the range of speeds possible if R = 100m, 0(theta)=10, and [mu]=0.10 (slippery conditions)????

    2.) In a popular amusement park ride, a rotating cylinder of radium 3.00m is set in rotation at an angular speed of 5.00rad/s. The floor then drops away, leaving the riders suspended against the wall in a vertical position. What minimum coefficient of friction between a rdier's clothing and the wall is needed to keep the rider from slipping?????? (hint: recall that the magnitude of the max force of static friction is equal to [mu]n, where n is the normal force - in this case, the force causing the centripetal acceleration.

    DAMN YOU ROTATIONAL MOTION AND CENTRIPETAL ACCELERATION. I HATE YOU!!$!$!)(
     
  2. jcsd
  3. Dec 3, 2003 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Well, take a crack at them and show your work. Demonstrate that you know something about Fnet = ma, centripetal acceleration, and friction.

    Start, as always, by identifying all the forces acting on the objects in question. (Car in 1; rider in 2) Have fun!
     
  4. Dec 3, 2003 #3

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Don't look all that "super-hard" to me- just apply the formulas that you already know:

    1. F= ma and, for a friction coefficient of μ, F= mμ. Since the road is banked at angle θ, there is a force down the slope of mg cos(&theta). In order not to slip downward, You must have
    ma> mg cos(&theta)- m&mu; and in order not to slip upward, you must have ma< mg cos(&theta)+ m&mu; You also should know the formula for the acceleration of a car going around a circle at constant speed. Put that in for a and solve for v.

    2. Friction force is &mu; time "normal force". In this case the normal force is ma where a is the "acceleration" due to the rotation around a circle at constant speed (you'll need that formula again).
    The friction force, &mu;(ma) must be at least the force of gravity, mg. Solve &mu;ma= mg for &mu;

    Yeah, It's just awful when people expect you to actually learn how to apply formulas!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: 2 Super Hard Rotational Motion Problems
  1. Hard 2d motion problem (Replies: 1)

Loading...