# Minimum coefficient of friction to keep cars from sliding off the road

#### rockchalk1312

A banked circular highway curve is designed for traffic moving at 61 km/h. The radius of the curve is 201 m. Traffic is moving along the highway at 44 km/h on a rainy day. What is the minimum coefficient of friction between tires and road that will allow cars to take the turn without sliding off the road? (Assume the cars do not have negative lift.)

Fk=ukFn
Fs, max=usFn
F=mv^2/R

Honestly no idea at how to attempt it. Although I did find that θ needed to be:
tanθ=v^2/gR
tanθ=12.2^2/(9.8)(201)
θ=4.32°

Thank you for any help!

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#### tms

Re: Minimum coefficient of friction to keep cars from sliding off the

As always, the first step is to draw a diagram showing all the forces acting on the car.

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