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Finding the coefficient of static friction

  • #1

Homework Statement


If a curve with a radius of 85m is properly banked for a car traveling 65 km/h what must the coefficiant of static friction be for a car not to skid when traveling at 95km/h


Homework Equations


For this question i tried using a few equations such as centripical force, force friction where Ffric = UsFn aswell as (mv^2)/R = Ffric i also though the equation Tan(theta)=V^2D/Rg was pertanent.


The Attempt at a Solution


I set up a proportion of mv^2/R = Us(ma) and the masses canceled out so i was left with v^2/ra but i didnt really know where to go from here.
 

Answers and Replies

  • #2
123
1
Welcome to Physics Forum, although I am quite new too.
The car is moving on a banked curve. Did you take in account the part of the normal force that points towards the centre [tex]N_{x}[/tex]? Also, you should also break the friction force into components [tex]f_{x}[/tex] and [tex]f_{y}[/tex].
 
  • #3
Ok i set up my two force components and i have Fycos(theta)=mg and Fxsin(theta)=mv^2/r when dividing both components together you are left with tan(theta)=v^2/rg and when i plug in the numbers given after converting 95 km/h to m/s you get a static friction of .81 am i doing somthing wrong because it doesn't seem right
 
  • #4
123
1
Fycos(theta)=mg and Fxsin(theta)=mv^2/r
What did you mean by Fy and Fx?
 
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